Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of
cell growthThe term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells".-Cell populations:Cell populations go through a type of...
,
differentiationIn 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 single zygote to a complex system of...
and "
morphogenesisMorphogenesis , is the biological process that causes an organism to develop its shape. It is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation...
," which is the process that gives rise to
tissueTissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function...
s,
organIn biology and anatomy, an organ is a collection of tissues joined in structural unit to serve a common function ....
s and
anatomyAnatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy and plant anatomy...
.
Developmental biology is that branch of life science, which deals with the study of the process by which organisms grow and develop.
Related fields of study
EmbryologyEmbryology is the study of the development of an embryo. An embryo is defined as any organism in an early stage well before birth or hatching, or in plants, before germination occurs....
is a subfield, the study of organisms between the one-cell stage (generally, the
zygoteA zygote , or zygocyte, is the initial cell formed when a new organism is produced by means of sexual reproduction. A zygote is synthesized from the union of two gametes, and constitutes the first stage in a unique organism's development...
) and the end of the embryonic stage. Embryology was originally a more descriptive science until the 20th century. Embryology and developmental biology today deal with the various steps necessary for the correct and complete formation of the
bodyWith regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...
of a living organism.
The related field of
evolutionary developmental biologyEvolutionary developmental biology is a field of biology that compares the developmental processes of different animals and plants in an attempt to determine the ancestral relationship between organisms and how developmental processes evolved...
was formed largely in the 1990s and is a synthesis of findings from molecular developmental biology and
evolutionary biologyEvolutionary biology is a sub-field of biology concerned with the origin of species from a common descent and descent of species, as well as their change, multiplication and diversity over time. Someone who studies evolutionary biology is known as an evolutionary biologist...
which considers the diversity of organismal form in an evolutionary context.
Perspectives
Animal development is a spectacular process and represents a masterpiece of temporal and spatial control of gene expression. Developmental genetics is a very helpful process. It studies the effect that genes have in a phenotype. The findings of developmental biology can help to understand developmental malfunctions such as chromosomal aberrations, for example,
Down syndromeDown syndrome , Down's syndrome , trisomy 21, or trisomy G is a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British doctor who described the syndrome in 1866...
. An understanding of the specialization of
cellsThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
during embryogenesis may yield information on how to specialize
stem cellStem cells are cells found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiating into a diverse range of specialized cell types. Research in the stem cell field grew out of findings by Canadian...
s to specific tissues and organs, which could lead to the specific
cloningCloning in biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or organisms...
of organs for medical purposes. Another biologically important process that occurs during development is
apoptosisApoptosis is the process of programmed cell death that may occur in multicellular organisms. Programmed cell death involves a series of biochemical events leading to a characteristic cell morphology and death; in more specific terms, a series of biochemical events that lead to a variety of...
- programmed cell death or "suicide". For this reason, many developmental models are used to elucidate the
physiologyPhysiology is the science of the functioning of living systems. It is a subcategory of biology...
and molecular basis of this cellular process. Similarly, a deeper understanding of developmental biology can foster greater progress in the treatment of congenital disorders and diseases, e.g. studying human sex determination can lead to treatment for disorders such as
congenital adrenal hyperplasiaCongenital adrenal hyperplasia refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands ....
.
Developmental model organisms
Often used
model organismA model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms...
s in developmental biology include the following:
- Vertebrates
- Zebrafish Danio rerio
The zebrafish, Danio rerio, is a tropical freshwater fish belonging to the minnow family . It is a popular aquarium fish, frequently sold under the trade name zebra danio, and is an important vertebrate model organism in scientific research.- Taxonomy :The zebrafish is a derived member of the genus...
- Medakafish Oryzias latipes
Oryzias latipes, also known as Medaka and Japanese killifish, is a member of genus Oryzias , the only genus in the family Oryziinae. This rather small...
- Fugu (pufferfish
Tetraodontidae is a family of primarily marine and estuarine fish. The family includes many familiar species which are variously called puffers, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, and toadies...
) Takifugu rubripes
- Frog Xenopus laevis, Xenopus tropicalis
- Chicken Gallus gallus
- Mouse Mus musculus (Mammalian embryogenesis
Mammalian embryogenesis is the process of cell division and cellular differentiation during early prenatal development which leads to the development of a mammalian embryo.-Difference from human embryogenesis:...
)
- Invertebrates
- Lancelet
The lancelets are the modern representatives of the subphylum Cephalochordata, usually said to be the sister group of the craniates. They are usually found buried in sand in shallow parts of temperate or tropical seas. In Asia, they are harvested commercially as food for humans and domesticated...
Branchiostoma lanceolatum
- Ascidian Ciona intestinalis
Ciona intestinalis or vase tunicate is a Urochordata whose genome has been sequenced. It has become, over the past decade, a major experimental model for developmental biologists...
- Sea urchin Strongylocentrotus purpuratus
Strongylocentrotus purpuratus, or the purple sea urchin, is one of the sharp-spined sea urchin species. The spines are used as a means of defense against would-be predators. This urchin is deep purple in color, and grows to a diameter of about 4 inches...
- Roundworm Caenorhabditis elegans
Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
- Fruit fly Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is commonly known as the common fruit fly or vinegar fly. Starting from Charles W...
(Drosophila embryogenesisDrosophila has long been a favorite model system for geneticists and developmental biologists studying embryogenesis. The small size, short generation time, and large brood size makes it ideal for genetic studies. Transparent embryos facilitate developmental studies...
)
- Plants (Plant embryogenesis
Plant embryogenesis is the process that produces a plant embryo from a fertilised ovule by asymmetric cell division and the differentiation of undifferentiated cells into tissues and organs. It occurs during seed development, when the single-celled zygote undergoes a programed pattern of cell...
)
- Arabidopsis thaliana
Arabidopsis thaliana , is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, Arabidopsis is popular as a model organism in plant biology and genetics...
- Maize
Maize , is a herbaceous plant domesticated in Mesoamerica and subsequently spread throughout the American continents...
- Snapdragon Antirrhinum majus
Antirrhinum majus is a species of plants belonging to the genus Antirrhinum. It is native to the Mediterranean region, from Morocco and Portugal north to southern France, and east to Turkey and Syria...
- Other
- Slime mold Dictyostelium discoideum
Dictyostelium discoideum is a species of soil-living amoeba belonging to the phylum Mycetozoa. D. discoideum, commonly referred to as slime mold, is a primitive eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body within its...
Cell differentiation
DifferentiationIn 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 single zygote to a complex system of...
is the formation of
cell typeA cell type is a distinct morphological or functional form of cell. When a cell switches state from one cell type to another, it undergoes cellular differentiation. A complete list of distinct cell types in the adult human body may include about 210 distinct types....
s, from what is originally one cell – the
zygoteA zygote , or zygocyte, is the initial cell formed when a new organism is produced by means of sexual reproduction. A zygote is synthesized from the union of two gametes, and constitutes the first stage in a unique organism's development...
or
sporeIn biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions...
. The formation of cell types like nerve cells occurs with a number of intermediary, less differentiated cell types. A cell stays a certain cell type by maintaining a particular pattern of
gene expressionGene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as rRNA genes or tRNA genes, the product is a functional RNA...
. This depends on regulatory genes, e.g. for
transcription factorIn the field of molecular biology, a transcription factor is a protein that binds to specific DNA sequences and thereby controls the transfer of genetic information from DNA to mRNA...
s and signaling proteins. These can take part in self-perpetuating circuits in the
gene regulatory networkA gene regulatory network or genetic regulatory network is a collection of DNA segments in a cell whichinteract with each other and with other substances in the cell, thereby governing the rates at which genes in the network are transcribed into mRNA...
, circuits that can involve several cells that
communicateCell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue...
with each other. External signals can alter gene expression by activating a
receptorIn biochemistry, a receptor is a protein molecule, embedded in either the plasma membrane or cytoplasm of a cell, to which a mobile signaling molecule may attach...
, which triggers a signaling cascade that affects transcription factors. For example, the withdrawal of growth factors from
myoblastA myoblast is a type of progenitor cell that gives rise to myocytes. Myocyte, skeletal muscle cell and muscle fiber are synonymous terms.Skeletal muscle fibers are made when myoblasts fuse together; muscle fibers therefore have multiple nuclei .The fusion of myoblasts is specific to skeletal muscle...
s causes them to stop dividing and instead differentiate into muscle cells.
Embryonal development
EmbryogenesisEmbryogenesis is the process by which the embryo is formed and develops. It starts with the fertilization of the ovum which, after fertilization, is referred to as a zygote. The zygote undergoes rapid mitotic divisions with no significant growth and cellular differentiation, leading to...
is the step in the
life cycleA life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
after
fertilisationFertilisation , is the fusion of gametes to produce a new organism. In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo...
– the development of the
embryoAn embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
, starting from the
zygoteA zygote , or zygocyte, is the initial cell formed when a new organism is produced by means of sexual reproduction. A zygote is synthesized from the union of two gametes, and constitutes the first stage in a unique organism's development...
(fertilised egg). Organisms can differ drastically in the how embryo develops, especially when belong to different
phylaIn biology, a phylum ["Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states.] is a taxonomic rank below Kingdom and above Class...
. For example, embryonal development in placental mammals starts with
cleavageIn embryology, cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a...
of the zygote into eight uncommited cells, which then form a ball (
morulaA morula is an embryo at an early stage of embryonic development, consisting of cells in a solid ball contained within the zona pellucida.-Production:...
). The outer cells become the trophectoderm which will form the fetal part of the
placentaThe placenta is an organ unique to mammals that connects the developing fetus to the uterine wall. The placenta supplies the fetus with oxygen and food, and allows fetal waste to be disposed of via the maternal kidneys...
, while inner cells become the
inner cell massIn early embryogenesis of most eutherian mammals, the inner cell mass is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus...
that will form all other organs. In contrast, the
fruit flyDrosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is commonly known as the common fruit fly or vinegar fly. Starting from Charles W...
zygote first forms a sausage-shaped
syncytiumIn biology, a syncytium is a large cell-like structure filled with cytoplasm containing many nuclei. Most cells in all organisms have a single nucleus; syncytia are specialized forms used by various organisms in normal tissue.- Formation :A syncytium can form in two ways...
, which is still one cell but with many
cell nucleiIn cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as...
.
PatterningThe science of pattern formation deals with the visible, orderly outcomes of self-organisation and the common principles behind similar patterns....
is important for determining which cells develop which organs. This is mediated by signaling between adjacent cells by proteins on their surfaces, and by gradients of signaling molecules. An example is
retinoic acidRetinoic acid is the oxidized form of Vitamin A, with only partial vitamin A function. It functions in determining position along embryonic anterior/posterior axis in chordates...
, which forms a gradient in the head to tail direction in animals. Retinoic acid enters cells and activates Hox genes in a concentration-dependent manner – Hox genes differ in how much retinoic acid they require for activation. As Hox genes code for transcription factors, this causes discrete segments in the head to tail direction. This is important for e.g. the
segmentationSegmentation in biology refers to the division of some metazoan bodies and plant body plans into a series of semi-repetitive segments, and the question of the benefits and costs of doing so. As such, segmentation is related to the more general concept of modularity.Examples of segmented animals are...
of the
spineIn human anatomy, the vertebral column is a column usually consisting of 33 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso, separated by spinal discs...
in vertebrates.
Embryonal development does not always go right, and errors can result in birth defects or
miscarriageMiscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving, generally defined in humans at prior to 20 weeks of gestation...
. Often the reason is genetic (
mutationIn biology, a mutation is a randomly derived change to the nucleotide sequence of the genetic material of an organism.Mutations can be caused by copying errors in the genetic material during cell division, or by exposure to mutagens , or can be induced by the organism itself, by cellular processes...
or chromosome abnormality), but there can be environmental influence (teratogens). Abnormal development is also of evolutionary interest as it provides a mechanism for changes in
body planA body plan is essentially the blueprint for the way the body of an organism is laid out. An organism's symmetry,
(
see evolutionary developmental biologyEvolutionary developmental biology is a field of biology that compares the developmental processes of different animals and plants in an attempt to determine the ancestral relationship between organisms and how developmental processes evolved...
).
Growth
Growth is the enlargement of a tissue or organism. Growth continues after the embryonal stage, and occurs through
cell proliferationThe term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells".-Cell populations:Cell populations go through a type of...
, enlargement of cells or accumulation of extracellular material. In plants, growth results in an adult organism that is strikingly different from the embryo. The proliferating cells tend to be distinct from differentiated cells (
see stem cellStem cells are cells found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiating into a diverse range of specialized cell types. Research in the stem cell field grew out of findings by Canadian...
and progenitor cellLike stem cells, progenitor cells have a capacity to differentiate into a specific type of cell. In contrast to stem cells, however, they are already far more specific: they are pushed to differentiate into their "target" cell...
). In some tissues proliferating cells are restricted to specialised areas, such as the growth plates of
boneBones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s. But some stem cells
migrateCell migration is a central process in the development and maintenance of multicellular organisms. Tissue formation during embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular directions to specific locations...
to where they are needed, such as
mesenchymal stem cellMesenchymal stem cells, or MSCs, are multipotent stem cells that can differentiate into a variety of cell types. Cell types that MSCs have been shown to differentiate into in vitro or in vivo include osteoblasts, chondrocytes, myocytes, adipocytes, endotheliums, and, as described lately,...
s which can migrate from the
bone marrowBone marrow is the flexible tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells. It constitutes 4% of total body weight, i.e...
to form e.g. muscle, bone or adipose tissue. The size of an organ frequently determines its growth, as in the case of the
liverThe liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
which grows back to its previous size if a part is removed.
Growth factorA growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes....
s, such as
fibroblast growth factorFibroblast growth factors, or FGFs, are a family of growth factors involved in angiogenesis, wound healing, and embryonic development. The FGFs are heparin-binding proteins and interactions with cell-surface associated heparan sulfate proteoglycans have been shown to be essential for FGF signal...
s in the animal embryo and
growth hormoneGrowth hormone is a protein-based poly-peptide hormone. It stimulates growth and cell reproduction and regeneration in humans and other animals. It is a 191-amino acid, single-chain polypeptide hormone that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of...
in juvenile mammals, also control the extent of growth.
Metamorphosis
Most animals have a
larvaA larva is a young form of animal with indirect development, going through or undergoing metamorphosis ....
l stage, with a body plan different from that of the adult organism. The larva abrubtly develops into an adult in a process called
metamorphosisMetamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
. For example,
caterpillarCaterpillars are the larval form of a member of the order Lepidoptera . They are mostly phytophagous in food habit, with some species being entomophagous. Caterpillars are voracious feeders and many of them are considered pests in agriculture...
s (butterfly larvae) are specialized for feeding whereas adult butterflies (
imagoIn biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...
s) are specialised for flight and reproduction. When the caterpillar has grown enough, it turns into an immobile
pupaA pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
. Here, the imago develops from
imaginal discAn imaginal disc is one of the parts of a holometabolous insect larva that will become a portion of the outside of the adult insect during the pupal transformation. Contained within the body of the larva, there are pairs of discs that will form, for instance, the wings or legs or antennae or other...
s found inside the larva.
Regeneration
RegenerationIn biology, an organism is said to regenerate a lost or damaged part if the part regrows so that the original function is restored.Regenerative capacity is inversely related to complexity: in general, the more complex an animal is the less regeneration it is capable of. Whereas newts, for example,...
is the reactivation of development so that a missing body part grows back. This phenomenon has been studied particularly in
salamanderSalamander is a common name of approximately 500 species of amphibians. They are typically characterized by their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant species are grouped together as the Urodela...
s, where the adults can reconstruct a whole limb after it has been amputated. Researchers hope to one day be able to induce regeneration in humans (
see regenerative medicineRegenerative Medicine is the process of creating living, functional tissues to repair or replace tissue or organ function lost due to age, disease, damage, or congenital defects. This field holds the promise of regenerating damaged tissues and organs in the body by stimulating previously...
). There is little spontaneous regeneration in adult humans, although the
liverThe liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
is a notable exception. Like for salamanders, the regeneration of the liver involves dedifferentiation of some cells to a more embryonal state.
Developmental systems biology
Computer simulation of multicellular development is a research methodology to understand the function of the very complex processes involved in the development of organisms. This includes simulation of cell signaling, multicell interactions and regulatory genomic networks in development of multicellular structures and processes (see
French flag modelThe French Flag Model is a conceptual definition of a morphogen, described by Lewis Wolpert in the 1960s . A morphogen is rigorously defined as a signaling molecule that acts directly on cells to produce specific cellular responses dependent on morphogen concentration...
or
Biological Physics of the Developing Embryo for literature).
Minimal genomes for minimal multicellular organisms may pave the way to understand such complex processes
in vivo.
See also
- Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
and PrecocialIn Biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born helpless. Extremely precocial species may be called "superprecocial."...
- Auxology
Auxology, sometimes called Auxanology , is a meta-term covering the study of all aspects of human physical growth; though it is also a fundamental of biology, generally...
- Body plan
A body plan is essentially the blueprint for the way the body of an organism is laid out. An organism's symmetry,
- Cell signaling
Cell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue...
- Embryogenesis
Embryogenesis is the process by which the embryo is formed and develops. It starts with the fertilization of the ovum which, after fertilization, is referred to as a zygote. The zygote undergoes rapid mitotic divisions with no significant growth and cellular differentiation, leading to...
- Embryology
Embryology is the study of the development of an embryo. An embryo is defined as any organism in an early stage well before birth or hatching, or in plants, before germination occurs....
- Evolutionary developmental biology
Evolutionary developmental biology is a field of biology that compares the developmental processes of different animals and plants in an attempt to determine the ancestral relationship between organisms and how developmental processes evolved...
- Plant evolutionary developmental biology
Evolutionary developmental biology refers to the study of developmental programs and patterns from an evolutionary perspective. It seeks to understand the various influences shaping the form and nature of life on the planet. Evo-devo arose as a separate branch of science only in the last decade...
- Fertilization
- Fish development
The development of fishes is unique in some specific aspects compared to the development of other animals.-Cleavage:Cleavage, or initial cell division, of the fish zygote is meroblastic, meaning the early cell divisions are not complete...
- Cell signaling networks
- Developmental noise
Developmental noise is a concept within developmental biology in which the phenotype varies between individuals even though both the genotypes and the environmental factors are the same for all of them....
- Enhancer
Enhancer can mean one of the following:* In genetics, an Enhancer is a short region of DNA that can bind proteins called an activator , binding of activators to this enhancer region can initiate the transcription of a gene that may be some distance away from the enhancer, or can even be on a...
- Enhanceosome
The enhanceosome is a protein complex that binds to the "enhancer" region of a gene, found upstream or downstream, of the promoter, or within a gene. It accelerates the gene's transcription...
- Gene regulatory network
A gene regulatory network or genetic regulatory network is a collection of DNA segments in a cell whichinteract with each other and with other substances in the cell, thereby governing the rates at which genes in the network are transcribed into mRNA...
- Promoter
In genetics, a promoter is a region of DNA that facilitates the transcription of a particular gene. Promoters are typically located near the genes they regulate, on the same strand and upstream .-Overview:...
- Signal transduction
In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another. Most processes of signal transduction involve ordered sequences of biochemical reactions inside the cell, which are carried out by enzymes and activated by second messengers,...
- Transcription factor
In the field of molecular biology, a transcription factor is a protein that binds to specific DNA sequences and thereby controls the transfer of genetic information from DNA to mRNA...
External links