Cloning

Cloning

Overview

Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s or plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s reproduce asexually
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...

. Cloning in biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

 refers to processes used to create copies of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 fragments (molecular cloning
Molecular cloning
Molecular cloning refers to a set of experimental methods in molecular biology that are used to assemble recombinant DNA molecules and to direct their replication within host organisms...

), cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 (cell cloning), or organisms. The term also refers to the production of multiple copies of a product such as digital media
Digital media
Digital media is a form of electronic media where data is stored in digital form. It can refer to the technical aspect of storage and transmission Digital media is a form of electronic media where data is stored in digital (as opposed to analog) form. It can refer to the technical aspect of...

 or software.

The term clone is derived from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 word κλών (klōn, “twig”), referring to the process whereby a new plant can be created from a twig.
Discussion
Ask a question about 'Cloning'
Start a new discussion about 'Cloning'
Answer questions from other users
Full Discussion Forum
 
Unanswered Questions
Encyclopedia

Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s or plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s reproduce asexually
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...

. Cloning in biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

 refers to processes used to create copies of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 fragments (molecular cloning
Molecular cloning
Molecular cloning refers to a set of experimental methods in molecular biology that are used to assemble recombinant DNA molecules and to direct their replication within host organisms...

), cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 (cell cloning), or organisms. The term also refers to the production of multiple copies of a product such as digital media
Digital media
Digital media is a form of electronic media where data is stored in digital form. It can refer to the technical aspect of storage and transmission Digital media is a form of electronic media where data is stored in digital (as opposed to analog) form. It can refer to the technical aspect of...

 or software.

The term clone is derived from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 word κλών (klōn, “twig”), referring to the process whereby a new plant can be created from a twig. In horticulture
Horticulture
Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic...

, the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o". Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively.

In the United States, the human consumption of meat and other products from cloned animals was approved by the FDA on December 28, 2006, with no special labeling required. Cloned beef and other products have since been regularly consumed in the US without distinction. Such practice has met strong resistance in other regions, such as Europe, particularly over the labeling issue.

Molecular cloning



Molecular cloning refers to the process of making multiple molecules. Cloning is commonly used to amplify DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 fragments containing whole genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

, but it can also be used to amplify any DNA sequence such as promoters, non-coding sequences and randomly fragmented DNA. It is used in a wide array of biological experiments and practical applications ranging from genetic fingerprinting
Genetic fingerprinting
DNA profiling is a technique employed by forensic scientists to assist in the identification of individuals by their respective DNA profiles. DNA profiles are encrypted sets of numbers that reflect a person's DNA makeup, which can also be used as the person's identifier...

 to large scale protein production. Occasionally, the term cloning is misleadingly used to refer to the identification of the chromosomal
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

 location of a gene associated with a particular phenotype of interest, such as in positional cloning. In practice, localization of the gene to a chromosome or genomic region does not necessarily enable one to isolate or amplify the relevant genomic sequence. To amplify any DNA sequence in a living organism, that sequence must be linked to an origin of replication
Origin of replication
The origin of replication is a particular sequence in a genome at which replication is initiated. This can either be DNA replication in living organisms such as prokaryotes and eukaryotes, or RNA replication in RNA viruses, such as double-stranded RNA viruses...

, which is a sequence of DNA capable of directing the propagation of itself and any linked sequence. However, a number of other features are needed and a variety of specialised cloning vector
Cloning vector
A cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted. The insertion of the fragment into the cloning vector is carried out by treating the vehicle and the foreign DNA with a restriction enzyme that creates the same overhang, then ligating the fragments...

s (small piece of DNA into which a foreign DNA fragment can be inserted) exist that allow protein expression
Protein expression
Protein expression is a subcomponent of gene expression. It consists of the stages after DNA has been translated into polypeptide chains, which are ultimately folded into proteins...

, tagging, single stranded RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 and DNA production and a host of other manipulations.

Cloning of any DNA fragment essentially involves four steps
  1. fragmentation - breaking apart a strand of DNA
  2. ligation
    DNA ligase
    In molecular biology, DNA ligase is a specific type of enzyme, a ligase, that repairs single-stranded discontinuities in double stranded DNA molecules, in simple words strands that have double-strand break . Purified DNA ligase is used in gene cloning to join DNA molecules together...

     - gluing together pieces of DNA in a desired sequence
  3. transfection
    Transfection
    Transfection is the process of deliberately introducing nucleic acids into cells. The term is used notably for non-viral methods in eukaryotic cells...

     - inserting the newly formed pieces of DNA into cells
  4. screening/selection - selecting out the cells that were successfully transfected with the new DNA

Although these steps are invariable among cloning procedures a number of alternative routes can be selected, these are summarized as a 'cloning strategy'.

Initially, the DNA of interest needs to be isolated to provide a DNA segment of suitable size. Subsequently, a ligation procedure is used where the amplified fragment is inserted into a vector
Vector (molecular biology)
In molecular biology, a vector is a DNA molecule used as a vehicle to transfer foreign genetic material into another cell. The four major types of vectors are plasmids, viruses, cosmids, and artificial chromosomes...

 (piece of DNA). The vector (which is frequently circular) is linearised using restriction enzyme
Restriction enzyme
A Restriction Enzyme is an enzyme that cuts double-stranded DNA at specific recognition nucleotide sequences known as restriction sites. Such enzymes, found in bacteria and archaea, are thought to have evolved to provide a defense mechanism against invading viruses...

s, and incubated with the fragment of interest under appropriate conditions with an enzyme called DNA ligase
DNA ligase
In molecular biology, DNA ligase is a specific type of enzyme, a ligase, that repairs single-stranded discontinuities in double stranded DNA molecules, in simple words strands that have double-strand break . Purified DNA ligase is used in gene cloning to join DNA molecules together...

. Following ligation the vector with the insert of interest is transfected into cells. A number of alternative techniques are available, such as chemical sensitivation of cells, electroporation
Electroporation
Electroporation, or electropermeabilization, is a significant increase in the electrical conductivity and permeability of the cell plasma membrane caused by an externally applied electrical field...

, optical injection and biolistics. Finally, the transfected cells are cultured. As the aforementioned procedures are of particularly low efficiency, there is a need to identify the cells that have been successfully transfected with the vector construct containing the desired insertion sequence in the required orientation. Modern cloning vectors include selectable antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 resistance markers, which allow only cells in which the vector has been transfected, to grow. Additionally, the cloning vectors may contain colour selection markers, which provide blue/white screening (alpha-factor complementation) on X-gal
X-gal
X-gal is an organic compound consisting of galactose linked to a substituted indole. The compound was synthesized by Jerome Horwitz and collaborators in Detroit, MI, in 1964. The formal chemical name is often shortened to less accurate but also less cumbersome phrases such as bromochloroindoxyl...

 medium. Nevertheless, these selection steps do not absolutely guarantee that the DNA insert is present in the cells obtained. Further investigation of the resulting colonies must be required to confirm that cloning was successful. This may be accomplished by means of PCR, restriction fragment analysis and/or DNA sequencing
DNA sequencing
DNA sequencing includes several methods and technologies that are used for determining the order of the nucleotide bases—adenine, guanine, cytosine, and thymine—in a molecule of DNA....

.

Unicellular organisms



Cloning a cell means to derive a population of cells from a single cell. In the case of unicellular organisms such as bacteria and yeast, this process is remarkably simple and essentially only requires the inoculation
Inoculation
Inoculation is the placement of something that will grow or reproduce, and is most commonly used in respect of the introduction of a serum, vaccine, or antigenic substance into the body of a human or animal, especially to produce or boost immunity to a specific disease...

 of the appropriate medium. However, in the case of cell cultures from multi-cellular organisms, cell cloning is an arduous task as these cells will not readily grow in standard media.

A useful tissue culture technique used to clone distinct lineages of cell lines involves the use of cloning rings (cylinders). According to this technique, a single-cell suspension of cells that have been exposed to a mutagenic agent
Mutagen
In genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are therefore also likely to be carcinogens...

 or drug used to drive selection
Selection
In the context of evolution, certain traits or alleles of genes segregating within a population may be subject to selection. Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively—meaning they contribute more offspring to the...

 is plated at high dilution to create isolated colonies; each arising from a single and potentially clonal distinct cell. At an early growth stage when colonies consist of only a few of cells, sterile polystyrene
Polystyrene
Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...

 rings (cloning rings), which have been dipped in grease are placed over an individual colony and a small amount of trypsin
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...

 is added. Cloned cells are collected from inside the ring and transferred to a new vessel for further growth.

Cloning in stem cell research



Somatic cell nuclear transfer
Somatic cell nuclear transfer
In genetics and developmental biology, somatic-cell nuclear transfer is a laboratory technique for creating a clonal embryo, using an ovum with a donor nucleus . It can be used in embryonic stem cell research, or, potentially, in regenerative medicine where it is sometimes referred to as...

, known as SCNT, can also be used to create embryos for research or therapeutic purposes. The most likely purpose for this is to produce embryos for use in stem cell research. This process is also called "research cloning" or "therapeutic cloning." The goal is not to create cloned human beings (called "reproductive cloning"), but rather to harvest stem cells that can be used to study human development and to potentially treat disease. While a clonal human blastocyst has been created, stem cell lines are yet to be isolated from a clonal source.

Therapeutic cloning is achieved by creating embryonic stem cells in the hopes of treating diseases such as diabetes and Alzheimer’s. The process begins by taking out the nucleus that contains the DNA from an egg and putting it in a nucleus from an adult. In the case of someone with Alzheimer’s disease, the nucleus from a skin cell of that patient is placed into an empty egg. The reprogrammed cell begins to develop into an embryo because the egg reacts with the transferred nucleus. The embryo will become genetically identical to the patient. The embryo will then form a blastocyst which has the potential to form/become any cell in the body.

The reason why SCNT is used for cloning is because somatic cells can be easily acquired and cultured in the lab. This process can either add or delete specific genomes of farm animals. A key point to remember is that cloning is achieved when the oocyte maintains its normal functions and instead of using sperm and egg genomes to replicate, the oocyte is inserted into the donor’s somatic cell nucleus. The oocyte will react on the somatic cell nucleus, the same way it would on sperm cells.

SCNT Process
The process of cloning a particular farm animal using SCNT is relatively the same for all animals. The first step is to collect the somatic cells from the animal that will be cloned. The somatic cells could be used immediately or stored in the laboratory for later use. The hardest part of SCNT is removing maternal DNA from an oocyte at metaphase II. Once this has been done, the somatic nucleus can be inserted into an egg cytoplasm. This creates a one-cell embryo. The grouped somatic cell and egg cytoplasm are then introduced to an electrical current. This energy will hopefully allow the cloned embryo to begin development. The successfully developed embryos are then placed in surrogate recipients, such as a cow or sheep in the case of farm animals.

Applications of SCNT
SCNT is seen to be a great method for producing agriculture animals for food consumption. It successfully cloned sheep, cattle, goats, and pigs. Another benefit is SCNT is seen as a solution to clone endangered species that are on the verge of going extinct.

Limitations of SCNT
Stresses placed on both the egg cell and the introduced nucleus are enormous, leading to a high loss in resulting cells. For example, Dolly the sheep was born after 277 eggs were used for SCNT, which created 29 viable embryos. Only three of these embryos survived until birth, and only one survived to adulthood. As the procedure currently cannot be automated, but has to be performed manually under a microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

, SCNT is very resource intensive. The biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

 involved in reprogramming the differentiated
Cellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...

 somatic cell nucleus and activating the recipient egg is also far from understood.

In SCNT, not all of the donor cell's genetic information is transferred, as the donor cell's mitochondria that contain their own mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

 are left behind. The resulting hybrid cells retain those mitochondrial structures which originally belonged to the egg. As a consequence, clones such as Dolly that are born from SCNT are not perfect copies of the donor of the nucleus.

Organism cloning



Organism cloning (also called reproductive cloning) refers to the procedure of creating a new multicellular organism, genetically identical to another. In essence this form of cloning is an asexual method of reproduction, where fertilization or inter-gamete contact does not take place. Asexual reproduction is a naturally occurring phenomenon in many species, including most plants (see vegetative reproduction
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...

) and some insects. Scientists have made some major achievements with cloning, including the asexual reproduction of sheep and cows. There is a lot of ethical debate over whether or not cloning should be used. However, cloning, or asexual propagation, has been common practice in the horticultural world for hundreds of years.

Horticultural


The term clone is used in horticulture to refer to descendants of a single plant which were produced by vegetative reproduction
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...

 or apomixis
Apomixis
In botany, apomixis was defined by Winkler as replacement of the normal sexual reproduction by asexual reproduction, without fertilization. This definition notably does not mention meiosis...

. Many horticultural plant cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

s are clones, having been derived from a single individual, multiplied by some process other than sexual reproduction. As an example, some European cultivars of grape
Grape
A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

s represent clones that have been propagated for over two millennia. Other examples are potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

 and banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

. Grafting
Grafting
Grafting is a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join together. This vascular joining is called inosculation...

 can be regarded as cloning, since all the shoots and branches coming from the graft are genetically a clone of a single individual, but this particular kind of cloning has not come under ethical
Ethics
Ethics, also known as moral philosophy, is a branch of philosophy that addresses questions about morality—that is, concepts such as good and evil, right and wrong, virtue and vice, justice and crime, etc.Major branches of ethics include:...

 scrutiny and is generally treated as an entirely different kind of operation.

Many tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s, shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s, vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...

s, fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s and other herbaceous perennials form clonal colonies
Clonal colony
A clonal colony or genet is a group of genetically identical individuals that have grown in a given location, all originating vegetatively from a single ancestor. In plants, an individual in such a population is referred to as a ramet...

. Parts of a large clonal colony often become detached from the parent, termed fragmentation
Fragmentation (cell biology)
In cell biology, fragmentation is the breaking apart of cells or cell organelles into smaller parts. Fragmentation may serve as a normal function for the cell, but may also be the result of a disorder.-Function:...

, to form separate individuals. Some plants e.g. dandelion also form seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s asexually, termed apomixis
Apomixis
In botany, apomixis was defined by Winkler as replacement of the normal sexual reproduction by asexual reproduction, without fertilization. This definition notably does not mention meiosis...

, resulting in clonal populations of genetically identical individuals.

Parthenogenesis


Clonal derivation exists in nature in some animal species and is referred to as parthenogenesis
Parthenogenesis
Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...

 (reproduction of an organism by itself without a mate). This is an asexual form of reproduction that is only found in females of some insects, crustaceans and lizards. The growth and development occurs without fertilization by a male. In plants, parthenogenesis means the development of an embryo from an unfertilized egg cell, and is a component process of apomixis. In species that use the XY sex-determination system
XY sex-determination system
The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects and some plants . In this system, females have two of the same kind of sex chromosome , and are called the homogametic sex. Males have two distinct sex chromosomes , and are called...

, the offspring will always be female. An example is the "Little Fire Ant
Fire ant
Fire ants are a variety of stinging ants with over 285 species worldwide. They have several common names, including ginger ants, tropical fire ants and red ants.- Appearance :...

" (Wasmannia auropunctata), which is native to Central
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 but has spread throughout many tropical environments.

Artificial cloning of organisms


Artificial cloning of organisms may also be called reproductive cloning.

Methods


Reproductive cloning generally uses "somatic cell nuclear transfer
Somatic cell nuclear transfer
In genetics and developmental biology, somatic-cell nuclear transfer is a laboratory technique for creating a clonal embryo, using an ovum with a donor nucleus . It can be used in embryonic stem cell research, or, potentially, in regenerative medicine where it is sometimes referred to as...

" (SCNT) to create animals that are genetically identical. This process entails the transfer of a nucleus from a donor adult cell (somatic cell) to an egg that has no nucleus. If the egg begins to divide normally it is transferred into the uterus of the surrogate mother. Such clones are not strictly identical since the somatic cells may contain mutations in their nuclear DNA. Additionally, the mitochondria
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...

 in the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

 also contains DNA and during SCNT this DNA is wholly from the donor egg, thus the mitochondrial
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...

 genome is not the same as that of the nucleus donor cell from which it was produced. This may have important implications for cross-species nuclear transfer in which nuclear-mitochondrial incompatibilities may lead to death.

Artificial embryo splitting or embryo twinning may also be used as a method of cloning, where an embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 is split in the maturation before embryo transfer
Embryo transfer
Embryo transfer refers to a step in the process of assisted reproduction in which embryos are placed into the uterus of a female with the intent to establish a pregnancy...

. It is optimally performed at the 6- to 8-cell stage, where it can be used as an expansion of IVF to increase the number of available embryos. If both embryos are successful, it gives rise to monozygotic (identical) twins.
Obtaining Blastocysts

A blastocyst
Blastocyst
The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula. It is a specifically mammalian example of a blastula. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast,...

 is formed in the early stage of the development of an embryo. During cloning process, the blastocyst cells often are obtained by scientists 5 days after the egg has been divided.

Dolly the Sheep



Dolly, a Finn-Dorset ewe
Domestic sheep
Sheep are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name "sheep" applies to many species in the genus Ovis, in everyday usage it almost always refers to Ovis aries...

, was the first mammal to have been successfully cloned from an adult cell. Dolly was formed by taking a cell from the udder of her biological mother. Her embryo was created by taking the cell and inserting it into a sheep ovum. The embryo was then placed inside a female sheep that went through a normal pregnancy. She was cloned at the Roslin Institute in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 and lived there from her birth in 1996 until her death in 2003 when she was six. Her stuffed remains
Taxidermy
Taxidermy is the act of mounting or reproducing dead animals for display or for other sources of study. Taxidermy can be done on all vertebrate species of animals, including mammals, birds, fish, reptiles, and amphibians...

 were placed at Edinburgh's Royal Museum, part of the National Museums of Scotland
National Museums of Scotland
National Museums Scotland is the organization that runs several national museums of Scotland. It is one of the country's National Collections, and holds internationally important collections of natural sciences, decorative arts, world cultures, science and technology, and Scottish history and...

.

Dolly was publicly significant because the effort showed that the genetic material from a specific adult cell, programmed to express only a distinct subset of its genes, can be reprogrammed to grow an entirely new organism. Before this demonstration, it had been shown by John Gurdon that nuclei from differentiated cells could give rise to an entire organism after transplantation into an enucleated egg. However, this concept was not yet demonstrated in a mamallian system.

Cloning Dolly the sheep had a low success rate per fertilized egg; she was born after 237 eggs were used to create 29 embryos, which only produced three lambs at birth, only one of which lived. Seventy calves have been created and one third of them died young; Prometea
Prometea
Prometea is a Haflinger foal, the first cloned horse and the first to be born from and carried by its cloning mother. Her birth was announced publicly on August 6, 2003. Born 36 kg after a natural delivery and a full-term pregnancy in Laboratory of Reproductive Technology, Cremona, Italy, Prometea...

 took 277 attempts. Notably, although the first clones were frogs, no adult cloned frog has yet been produced from a somatic adult nucleus donor cell.

There were early claims that Dolly the Sheep
Dolly the Sheep
Dolly was a female domestic sheep, and the first mammal to be cloned from an adult somatic cell, using the process of nuclear transfer. She was cloned by Ian Wilmut, Keith Campbell and colleagues at the Roslin Institute near Edinburgh in Scotland...

 had pathologies resembling accelerated aging. Scientists speculated that Dolly's death in 2003 was related to the shortening of telomere
Telomere
A telomere is a region of repetitive DNA sequences at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Its name is derived from the Greek nouns telos "end" and merοs "part"...

s, DNA-protein complexes that protect the end of linear chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

s. However, other researchers, including Ian Wilmut
Ian Wilmut
Sir Ian Wilmut, OBE FRS FMedSci FRSE is an English embryologist and is currently Director of the Medical Research Council Centre for Regenerative Medicine at the University of Edinburgh. He is best known as the leader of the research group that in 1996 first cloned a mammal from an adult somatic...

 who led the team that successfully cloned Dolly, argue that Dolly's early death due to respiratory infection was unrelated to deficiencies with the cloning process.

Water buffalo


On September 15, 2007, the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

 announced its development
New product development
In business and engineering, new product development is the term used to describe the complete process of bringing a new product to market. A product is a set of benefits offered for exchange and can be tangible or intangible...

 of Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

’s first cloned water buffalo
Water buffalo
The water buffalo is a domesticated bovid widely kept in Asia, Europe and South America.Water buffalo can also refer to:*Wild water buffalo , the wild ancestor of the domestic water buffalo...

. The Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), under the Department of Science and Technology in Los Baños
Los Baños, Laguna
The Nature and Science City of Los Baños is a 1st class urban city in the province of Laguna, Philippines. According to the latest census, it has a population of 98,631 inhabitants in 17,030 households...

, Laguna approved this project
Project
A project in business and science is typically defined as a collaborative enterprise, frequently involving research or design, that is carefully planned to achieve a particular aim. Projects can be further defined as temporary rather than permanent social systems that are constituted by teams...

.

Species cloned



The modern cloning techniques involving nuclear transfer
Nuclear transfer
Nuclear Transfer is a form of cloning. The steps involve removing the DNA from an oocyte , and injecting the nucleus which contains the DNA to be cloned. In rare instances, the newly constructed cell will divide normally, replicating the new DNA while remaining in a pluripotent state...

 have been successfully performed on several species. Landmark experiments in chronological order:
  • Tadpole
    Tadpole
    A tadpole or polliwog is the wholly aquatic larval stage in the life cycle of an amphibian, particularly that of a frog or toad.- Appellation :...

    : (1952) Many scientists questioned whether cloning had actually occurred and unpublished experiments by other labs were not able to reproduce the reported results.
  • Carp
    Carp
    Carp are various species of oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes, Siluriformes and Gymnotiformes to create the superorder Ostariophysi, since these groups have certain...

    : (1963) In China
    China
    Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

    , embryologist Tong Dizhou
    Tong Dizhou
    Tong Dizhou was a Chinese embryologist remembered for his contributions to the field of cloning. He was the former vice president of Chinese Academy of Science-Biography:...

     produced the world's first cloned fish by inserting the DNA from a cell of a male carp into an egg from a female carp. He published the findings in a Chinese science journal.
  • Mice
    MICE
    -Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...

    : (1986) A mouse was the first mammal successfully cloned from an early embryonic cell. Soviet
    Soviet Union
    The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

     scientists Chaylakhyan, Veprencev, Sviridova, and Nikitin had the mouse "Masha" cloned. Research was published in the magazine "Biofizika" volume ХХХII, issue 5 of 1987.
  • Sheep
    Domestic sheep
    Sheep are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name "sheep" applies to many species in the genus Ovis, in everyday usage it almost always refers to Ovis aries...

    : (1996) From early embryonic cells by Steen Willadsen. Megan and Morag cloned from differentiated embryonic cells in June 1995 and Dolly the sheep
    Dolly the Sheep
    Dolly was a female domestic sheep, and the first mammal to be cloned from an adult somatic cell, using the process of nuclear transfer. She was cloned by Ian Wilmut, Keith Campbell and colleagues at the Roslin Institute near Edinburgh in Scotland...

     from a somatic cell in 1997.
  • Rhesus Monkey: Tetra
    Tetra (monkey)
    Tetra is a Rhesus macaque that was created through a cloning technique called "embryo splitting". She is the first cloned primate, and was created by a team led by Professor Gerald Schatten of the Oregon National Primate Research Center....

     (January 2000) from embryo splitting
  • Gaur
    Gaur
    The gaur , also called Indian bison, is a large bovine native to South Asia and Southeast Asia. The species is listed as vulnerable on the IUCN Red List since 1986 as the population decline in parts of the species' range is likely to be well over 70% over the last three generations...

    : (2001) was the first endangered species cloned.
  • Cattle
    Cattle
    Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

    : Alpha and Beta (males, 2001) and (2005) Brazil
  • Cat
    Cat
    The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

    : CopyCat
    CC (cat)
    CC, for "CopyCat" or "Carbon Copy" , is a brown tabby and white domestic shorthair and the first cloned pet. CC's surrogate mother was a tabby, but her genetic donor, Rainbow, was a calico domestic shorthair...

     "CC" (female, late 2001), Little Nicky
    Little Nicky (cat)
    Little Nicky is the first commercially produced cat clone. He was produced from the DNA of a 17-year-old Maine Coon cat named Nicky who died in 2003...

    , 2004, was the first cat cloned for commercial reasons
  • Dog
    Dog
    The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

    : Snuppy
    Snuppy
    Snuppy is an Afghan hound, credited with being the world's first cloned dog. The puppy was created using the cell of an ear from an adult Afghan hound and involved 123 surrogate mothers, of which only three produced pups...

    , a male Afghan hound
    Afghan Hound
    The Afghan Hound is one of the oldest sighthound dog breeds. Distinguished by its thick, fine, silky coat and its tail with a ring curl at the end, the breed acquired its unique features in the cold mountains of Afghanistan, where it was originally used to hunt hares and gazelles by coursing them....

     was the first cloned dog (2005).
  • Rat
    Rat
    Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

    : Ralph, the first cloned rat (2003)
  • Mule
    Mule
    A mule is the offspring of a male donkey and a female horse. Horses and donkeys are different species, with different numbers of chromosomes. Of the two F1 hybrids between these two species, a mule is easier to obtain than a hinny...

    : Idaho Gem
    Idaho Gem
    The mule Idaho Gem was the first equine and first cloned mule.He resulted from the collaboration of Dr. Gordon Woods and Dr. Dirk Vanderwall of the Northwest Equine Reproduction Laboratory at the University of Idaho and Dr. Ken White of Utah State University...

    , a john mule born 4 May 2003, was the first horse-family clone.
  • Horse
    Horse
    The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

    : Prometea
    Prometea
    Prometea is a Haflinger foal, the first cloned horse and the first to be born from and carried by its cloning mother. Her birth was announced publicly on August 6, 2003. Born 36 kg after a natural delivery and a full-term pregnancy in Laboratory of Reproductive Technology, Cremona, Italy, Prometea...

    , a Haflinger female born 28 May 2003, was the first horse clone.
  • Water Buffalo
    Water Buffalo
    The water buffalo or domestic Asian water buffalo is a large bovine animal, frequently used as livestock in southern Asia, and also widely in South America, southern Europe, northern Africa, and elsewhere....

    : Samrupa was the first cloned water buffalo. It was born on February 6, 2009, at India
    India
    India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

    's Karnal National Diary Research Institute but died five days later due to lung infection.
  • Pyrenean Ibex
    Pyrenean Ibex
    The Pyrenean Ibex is an ibex, one of the two extinct subspecies of Spanish Ibex. The subspecies once ranged across the Pyrenees in France and Spain and the surrounding area, including the Basque Country, Navarre, north Aragon and north Catalonia. A few hundred years ago they were numerous, but by...

     (2009) was the first "extinct" animal (while the species is not extinct, nor even endangered, no living examples of the Pyrenean subspecies had been known since 2000) to be cloned back to life; the clone lived for seven minutes before dying of lung defects.
  • Camel
    Camel
    A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...

    : (2009) Injaz
    Injaz
    Injaz is a female dromedary camel, credited with being the world's first cloned camel. Dr. Nisar Ahmad Wani, a veterinarian embryologist at the Camel Reproduction Center in Dubai, United Arab Emirates, announced on April 14, 2009, that the cloned camel was born after an "uncomplicated" gestation...

    , is the first cloned camel.

Human cloning



Human cloning is the creation of a genetically
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 identical copy of an existing or previously existing human
Human
Humans are the only living species in the Homo genus...

. The term is generally used to refer to artificial human cloning; human clones in the form of identical twins are commonplace, with their cloning occurring during the natural process of reproduction. There are two commonly discussed types of human cloning: therapeutic cloning and reproductive cloning. Therapeutic cloning involves cloning adult cells for use in medicine and is an active area of research. Reproductive cloning would involve making cloned humans. A third type of cloning called replacement cloning is a theoretical possibility, and would be a combination of therapeutic and reproductive cloning. Replacement cloning would entail the replacement of an extensively damaged, failed, or failing body through cloning followed by whole or partial brain transplant.

The various forms of human cloning are controversial. There have been numerous demands for all progress in the human cloning field to be halted. Most scientific, governmental and religious organizations oppose reproductive cloning. The American Association for the Advancement of Science
American Association for the Advancement of Science
The American Association for the Advancement of Science is an international non-profit organization with the stated goals of promoting cooperation among scientists, defending scientific freedom, encouraging scientific responsibility, and supporting scientific education and science outreach for the...

 (AAAS) and other scientific organizations have made public statements suggesting that human reproductive cloning be banned until safety issues are resolved. Serious ethical concerns
Bioethics
Bioethics is the study of controversial ethics brought about by advances in biology and medicine. Bioethicists are concerned with the ethical questions that arise in the relationships among life sciences, biotechnology, medicine, politics, law, and philosophy....

 have been raised by the future possibility of harvesting organs from clones. Some people have considered the idea of growing organs separately from a human organism - in doing this, a new organ supply could be established without the moral implications of harvesting them from humans. Research is also being done on the idea of growing organs that are biologically acceptable to the human body inside of other organisms, such as pigs or cows, then transplanting them to humans, a form of xenotransplantation
Xenotransplantation
Xenotransplantation , is the transplantation of living cells, tissues or organs from one species to another. Such cells, tissues or organs are called xenografts or xenotransplants...

.

The first hybrid human clone was created in November 1998, by Advanced Cell Technologies. It was created from a man's leg cell, and a cow's egg whose DNA was removed. It was destroyed after 12 days. Since a normal embryo implants at 14 days, Dr Robert Lanza
Robert Lanza
Robert Paul Lanza is an American Doctor of Medicine, scientist, Chief Scientific Officer of Advanced Cell Technology and Adjunct Professor at the Institute for Regenerative Medicine, Wake Forest University School of Medicine....

, ACT's director of tissue engineering, told the Daily Mail newspaper that the embryo could not be seen as a person before 14 days. While making an embryo, which may have resulted in a complete human had it been allowed to come to term, according to ACT: "[ACT's] aim was 'therapeutic cloning' not 'reproductive cloning'"

On January, 2008, Wood and Andrew French, Stemagen's chief scientific officer in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, announced that they successfully created the first 5 mature human embryos using DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 from adult skin cells, aiming to provide a source of viable embryonic stem cells. Dr. Samuel Wood
Samuel H. Wood
Samuel H. Wood is a scientist noted for donating DNA that was used in somatic cell nuclear transfer to produce mature human embryos that were clones of Dr. Wood...

 and a colleague donated skin cells, and DNA from those cells was transferred to human eggs. It is not clear if the embryos produced would have been capable of further development, but Dr. Wood stated that if that were possible, using the technology for reproductive cloning would be both unethical and illegal. The 5 cloned embryos, created in Stemagen Corporation lab, in La Jolla, were destroyed.

Ethical issues of cloning



Because of recent technological advancements, the cloning of animals (and potentially humans) has been an issue. The Catholic Church and many religious organizations oppose all forms of cloning, on the grounds that life begins at conception. Judaism does not equate life with conception and, though some question the wisdom of cloning, Orthodox Judaism
Orthodox Judaism
Orthodox Judaism , is the approach to Judaism which adheres to the traditional interpretation and application of the laws and ethics of the Torah as legislated in the Talmudic texts by the Sanhedrin and subsequently developed and applied by the later authorities known as the Gaonim, Rishonim, and...

 rabbis generally find no firm reason in Jewish law and ethics to object to cloning. From the standpoint of classical liberalism
Liberalism
Liberalism is the belief in the importance of liberty and equal rights. Liberals espouse a wide array of views depending on their understanding of these principles, but generally, liberals support ideas such as constitutionalism, liberal democracy, free and fair elections, human rights,...

, concerns also exist regarding the protection of the identity of the individual and the right to protect one's genetic identity.

Gregory Stock
Gregory Stock
Gregory Stock is a biophysicist, best-selling author, biotech entrepreneur, and the former director of the Program on Medicine, Technology and Society at UCLA’s School of Medicine...

 is a scientist and outspoken critic against restrictions on cloning research. Bioethicist Gregory Pence
Gregory Pence
Gregory E. Pence is a professor in the department of Philosophy at the University of Alabama at Birmingham. He is an expert in the field of medical ethics who has written several books and has testified before the United States Congress and the California Senate about cloning and reproductive...

 also attacks the idea of criminalizing attempts to clone humans.

The social implications of an artificial human production scheme were famously explored in Aldous Huxley
Aldous Huxley
Aldous Leonard Huxley was an English writer and one of the most prominent members of the famous Huxley family. Best known for his novels including Brave New World and a wide-ranging output of essays, Huxley also edited the magazine Oxford Poetry, and published short stories, poetry, travel...

's novel Brave New World
Brave New World
Brave New World is Aldous Huxley's fifth novel, written in 1931 and published in 1932. Set in London of AD 2540 , the novel anticipates developments in reproductive technology and sleep-learning that combine to change society. The future society is an embodiment of the ideals that form the basis of...

.


On December 28, 2006, the U.S. Food and Drug Administration (FDA) approved the consumption of meat and other products from cloned animals. Cloned-animal products were said to be virtually indistinguishable from the non-cloned animals. Furthermore, companies would not be required to provide labels
Food labeling regulations
Many countries have Food labeling regulations -- see the following articles for more information:*United Kingdom food labeling regulations*Fair Packaging and Labeling Act -- a 1966 law passed in the USA....

 informing the consumer that the meat comes from a cloned animal.

Critics have raised objections to the FDA's approval of cloned-animal products for human consumption, arguing that the FDA's research was inadequate, inappropriately limited, and of questionable scientific validity. Several consumer-advocate groups are working to encourage a tracking program that would allow consumers to become more aware of cloned-animal products within their food.

Joseph Mendelson, legal director of the Center for Food Safety
Center for Food Safety
The Center for Food Safety is a U.S. non-profit organization, based in Washington, D.C., that also maintains an office in San Francisco, CA...

, said that cloned food still should be labeled since safety and ethical issues about it remain questionable.

Carol Tucker Foreman, director of food policy
Food policy
Food policy is an area of public policy concerning the production, distribution, and consumption of food. The policy consists of setting goals for food production, processing, marketing, availability, access, utilization and consumption, and describes the processes for achieving these goals...

 at the Consumer Federation of America
Consumer Federation of America
The Consumer Federation of America is a non-profit organization founded in 1968 to advance consumer interests through research, education and advocacy....

, stated that FDA does not consider the fact that the results of some studies revealed that cloned animals have increased rates of mortality and deformity at birth.

Another concern is that the biotechnologies used on animals may someday be used on humans. Some people may be more open to the idea of cloning of animals because most western countries have passed legislation against cloning humans, yet only a few countries passed legislation against cloning animals.

Possible Abnormalities due to Cloning

Researchers have found several abnormalities in cloned organisms, particularly in mice. The cloned organism may be born normal and resemble its non-cloned counterpart, but majority of the time will express changes in its genome later on in life. The concern with cloning humans is that the changes in genomes may not only result in changes in appearance, but in psychological and personality changes as well. The theory behind this is that the biological blueprint of the genes is the same in cloned animals as it is in normal ones, but they are read and expressed incorrectly. DNA arrays were used to prove this claim in the research lab of Professor Rudolf Jaenisch. Jaenisch studied placentas from cloned mice and found that one in every 25 genes was expressed abnormally. Results of these abnormally expressed genes in the cloned mice were premature death, pneumonia, liver failure and obesity.

Cloning extinct and endangered species


Cloning, or more precisely, the reconstruction of functional DNA from extinct species has, for decades, been a dream of some scientists. The possible implications of this were dramatized
Biological issues in Jurassic Park
Jurassic Park, a book by Michael Crichton, with a film version directed by Steven Spielberg, revolves around the resurrection of dinosaurs via genetic engineering. Scientists and enthusiasts have brought up a number of issues with facts and feasibility...

 in the best-selling novel by Michael Crichton
Michael Crichton
John Michael Crichton , best known as Michael Crichton, was an American best-selling author, producer, director, and screenwriter, best known for his work in the science fiction, medical fiction, and thriller genres. His books have sold over 200 million copies worldwide, and many have been adapted...

 and high budget Hollywood thriller Jurassic Park
Jurassic Park (film)
Jurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg. The film is based on the novel of the same name by Michael Crichton. It stars Sam Neill, Laura Dern, Jeff Goldblum, Richard Attenborough, Martin Ferrero, and Bob Peck...

. In real life, one of the most anticipated targets for cloning was once the Woolly Mammoth
Woolly mammoth
The woolly mammoth , also called the tundra mammoth, is a species of mammoth. This animal is known from bones and frozen carcasses from northern North America and northern Eurasia with the best preserved carcasses in Siberia...

, but attempts to extract DNA from frozen mammoths have been unsuccessful, though a joint Russo-Japanese team is currently working toward this goal. And in January 2011, it was reported by Yomiuri Shimbun that a team of scientists headed by Akira Iritani of Kyoto University had built upon research by Dr. Wakayama, saying that they will extract DNA from a mammoth carcass that had been preserved in a Russian laboratory and insert it into the egg cells of an African elephant in hopes of producing a mammoth embryo. The researchers said they hoped to produce a baby mammoth within six years.

In 2001, a cow named Bessie gave birth to a cloned Asian gaur
Gaur
The gaur , also called Indian bison, is a large bovine native to South Asia and Southeast Asia. The species is listed as vulnerable on the IUCN Red List since 1986 as the population decline in parts of the species' range is likely to be well over 70% over the last three generations...

, an endangered species, but the calf died after two days. In 2003, a banteng
Banteng
The banteng , also known as tembadau, is a species of wild cattle found in Southeast Asia.Banteng have been domesticated in several places in Southeast Asia, and there are around 1.5 million domestic banteng, which are called Bali cattle. These animals are used as working animals and for their meat...

 was successfully cloned, followed by three African wildcats from a thawed frozen embryo. These successes provided hope that similar techniques (using surrogate mothers of another species) might be used to clone extinct species. Anticipating this possibility, tissue samples from the last bucardo (Pyrenean Ibex
Pyrenean Ibex
The Pyrenean Ibex is an ibex, one of the two extinct subspecies of Spanish Ibex. The subspecies once ranged across the Pyrenees in France and Spain and the surrounding area, including the Basque Country, Navarre, north Aragon and north Catalonia. A few hundred years ago they were numerous, but by...

) were frozen in liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...

 immediately after it died in 2000. Researchers are also considering cloning endangered species such as the giant panda, ocelot, and cheetah. The "Frozen Zoo
Frozen zoo
A frozen zoo is a storage facility in which genetic materials taken from animals are gathered and thereafter stored at very low temperatures for optimal preservation over a long period of time...

" at the San Diego Zoo
San Diego Zoo
The San Diego Zoo in Balboa Park, San Diego, California, is one of the most progressive zoos in the world, with over 4,000 animals of more than 800 species...

 now stores frozen tissue from the world's rarest and most endangered species.

In 2002, geneticists at the Australian Museum
Australian Museum
The Australian Museum is the oldest museum in Australia, with an international reputation in the fields of natural history and anthropology. It features collections of vertebrate and invertebrate zoology, as well as mineralogy, palaeontology, and anthropology...

 announced that they had replicated DNA of the Thylacine
Thylacine
The thylacine or ,also ;binomial name: Thylacinus cynocephalus, Greek for "dog-headed pouched one") was the largest known carnivorous marsupial of modern times. It is commonly known as the Tasmanian tiger or the Tasmanian wolf...

 (Tasmanian Tiger), extinct about 65 years previous, using polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....

. However, on February 15, 2005 the museum announced that it was stopping the project after tests showed the specimens' DNA had been too badly degraded by the (ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

) preservative. On 15 May 2005 it was announced that the Thylacine project would be revived, with new participation from researchers in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

 and Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....

.

In January 2009, for the first time, an extinct animal, the Pyrenean ibex mentioned above was cloned, at the Centre of Food Technology and Research of Aragon, using the preserved DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 of the skin samples from 2001 and domestic goat egg-cells. (The ibex died shortly after birth due to physical defects in its lungs.) One of the continuing obstacles in the attempt to clone extinct species is the need for nearly perfect DNA. Cloning from a single specimen could not create a viable breeding population in sexually reproducing animals. Furthermore, even if males and females were to be cloned, the question would remain open whether they would be viable at all in the absence of parents that could teach or show them their natural behavior.

Cloning endangered species is a highly ideological issue. Many conservation biologists
Conservation biology
Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...

 and environmentalist
Environmentalist
An environmentalist broadly supports the goals of the environmental movement, "a political and ethical movement that seeks to improve and protect the quality of the natural environment through changes to environmentally harmful human activities"...

s vehemently oppose cloning endangered species—mainly because they think it may deter donations to help preserve natural habitat and wild animal populations. The "rule-of-thumb" in animal conservation is that, if it is still feasible to conserve habitat and viable wild populations, breeding in captivity should not be undertaken in isolation.

In a 2006 review, David Ehrenfeld concluded that cloning in animal conservation is an experimental technology that, at its state in 2006, could not be expected to work except by pure chance and utterly failed a cost-benefit analysis
Cost-benefit analysis
Cost–benefit analysis , sometimes called benefit–cost analysis , is a systematic process for calculating and comparing benefits and costs of a project for two purposes: to determine if it is a sound investment , to see how it compares with alternate projects...

. Furthermore, he said, it is likely to siphon funds from established and working projects and does not address any of the issues underlying animal extinction (such as habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...

, hunting
Hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...

 or other overexploitation
Overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...

, and an impoverished gene pool). While cloning technologies are well-established and used on a regular basis in plant conservation, care must be taken to ensure genetic diversity. He concluded:

In science fiction


Cloning has been used in countless science fiction works throughout the years. Human cloning is usually the most popular kind that is used in these particular works, mainly due to fact that it brings up controversial questions of identity. For example, in C.J. Cherryh’s novel Cyteen
Cyteen
Cyteen is a Hugo Award-winning science fiction novel by C. J. Cherryh set in her Alliance-Union universe. The murder of a major Union politician and scientist has deep, long-lasting repercussions....

, Aldous Huxley’s novel Brave New World
Brave New World
Brave New World is Aldous Huxley's fifth novel, written in 1931 and published in 1932. Set in London of AD 2540 , the novel anticipates developments in reproductive technology and sleep-learning that combine to change society. The future society is an embodiment of the ideals that form the basis of...

, human cloning is a major plot device that not only drives the story along but also makes the reader think critically about what identity means.

Star Wars
Star Wars
Star Wars is an American epic space opera film series created by George Lucas. The first film in the series was originally released on May 25, 1977, under the title Star Wars, by 20th Century Fox, and became a worldwide pop culture phenomenon, followed by two sequels, released at three-year...

 also portrays human cloning in Star Wars Episode II: Attack of the Clones
Star Wars Episode II: Attack of the Clones
Star Wars Episode II: Attack of the Clones is a 2002 American epic space opera film directed by George Lucas and written by Lucas and Jonathan Hales. It is the fifth film to be released in the Star Wars saga and the second in terms of the series' internal chronology...

and Star Wars Episode III: Revenge of the Sith
Star Wars Episode III: Revenge of the Sith
Star Wars Episode III: Revenge of the Sith is a 2005 American epic space opera film written and directed by George Lucas. It is the sixth and final film released in the Star Wars saga and the third in terms of the series' internal chronology....

, in the form of the Grand Army of the Republic
Grand Army of the Republic
The Grand Army of the Republic was a fraternal organization composed of veterans of the Union Army, US Navy, US Marines and US Revenue Cutter Service who served in the American Civil War. Founded in 1866 in Decatur, Illinois, it was dissolved in 1956 when its last member died...

, an army of clone trooper
Clone trooper
The clone troopers of the Army of the Republic are soldiers in the fictional Star Wars universe, cloned from Jango Fett, a Mandalorian bounty hunter. They first appeared in Star Wars Episode II: Attack of the Clones, and returned in Star Wars Episode III: Revenge of the Sith where they were played...

s. The Expanded Universe also has numerous examples of cloning, including the Thrawn trilogy, The Hand of Thrawn duology, and Clone Wars
Clone Wars (Star Wars)
The Clone Wars are a series of fictional intragalactic battles in George Lucas's science fiction saga Star Wars. The conflict is first mentioned in the film Star Wars Episode IV: A New Hope , but no details are given , and the wars themselves are not featured until the series' fifth and sixth...

-era media.
Ishiguro's novel 'Never Let Me Go' also features the use of clones and can be seen as a critique of society.(Also The book Clone Codes)

External links