Chromosome 22 is one of the 23 pairs of
chromosomeA chromosome is an organized structure of DNA and protein that is 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...
s in
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
s. Humans normally have two copies of Chromosome 22. Chromosome 22 is the second smallest human chromosome, spanning about 49 million
base pairIn molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair . In the canonical Watson-Crick base pairing, adenine forms a base pair with thymine , as does guanine with cytosine in DNA. In RNA, thymine is replaced...
s (the building material of
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
) and representing between 1.5 and 2 % of the total DNA in
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...
.
In 1999, researchers working on the
Human Genome ProjectThe Human Genome Project was an international scientific research project with a primary goal to determine the sequence of chemical base pairs which make up DNA and to identify and map the approximately 20,000–25,000 genes of the human genome from both a physical and functional standpoint...
announced they had determined the sequence of base pairs that make up this chromosome.
Chromosome 22 is one of the 23 pairs of
chromosomeA chromosome is an organized structure of DNA and protein that is 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...
s in
humanHumans are bipedal primates belonging to the species Homo sapiens in Hominidae, the great ape family. They are the only surviving member of the genus Homo. Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving...
s. Humans normally have two copies of Chromosome 22. Chromosome 22 is the second smallest human chromosome, spanning about 49 million
base pairIn molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair . In the canonical Watson-Crick base pairing, adenine forms a base pair with thymine , as does guanine with cytosine in DNA. In RNA, thymine is replaced...
s (the building material of
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
) and representing between 1.5 and 2 % of the total DNA in
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...
.
In 1999, researchers working on the
Human Genome ProjectThe Human Genome Project was an international scientific research project with a primary goal to determine the sequence of chemical base pairs which make up DNA and to identify and map the approximately 20,000–25,000 genes of the human genome from both a physical and functional standpoint...
announced they had determined the sequence of base pairs that make up this chromosome. Chromosome 22 was the first human chromosome to be fully sequenced.
Identifying
geneA gene is the basic unit of heredity in a living organism. All living things depend on genes. Genes hold the information to build and maintain their cells and pass genetic traits to offspring...
s on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 22 contains about 693 genes.
Chromosome 22 was originally identified as the smallest chromosome, but after extensive research, researchers concluded that it was indeed chromosome 21. The chromosomes weren't renamed because of the popularity of chromosome 21 (being known as the chromosome that can lead to Down's Syndrome). For this reason, researchers did not rearrange the numbers on these chromosomes.
Genes
The following are some of the genes located on chromosome 22:
| Locus |
Gene |
Description |
Condition
>-
| |
IGL@ Immunoglobulin lambda locus, also known as IGL@, is a region on human chromosome 22 that contains genes for the lambda light chains of antibodies .- Function :...
|
light chain A light chain is the small polypeptide subunit of a protein complex such as a motor protein or an antibody .More specifically, it can refer to:* Immunoglobulin light chain* Ferritin light chain...
s of antibodiesAntibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses...
>-
| |
TBX1 TBX1 is a human gene that codes for the protein called T-box 1. Genes in the T-box family play important roles in the formation of tissues and organs during embryonic development. To carry out these roles, proteins made by this gene family bind to specific areas of DNA. By attaching to critical...
|
} || RTN4R ||
Reticulon 4 receptorReticulon 4 receptor also known as Nogo-66 Receptor is a protein which in humans is encoded by the RTN4R gene. This gene encodes the receptor for reticulon 4, oligodendrocytemyelin glycoprotein and myelin-associated glycoprotein...
||
SchizophreniaSchizophrenia , from the Greek roots skhizein and phrēn, phren- is a psychiatric diagnosis that describes a mental disorder characterized by abnormalities in the perception or expression of reality...
|-
| || COMT|| catechol-O-methyltransferase gene
|-
| || NEFH|| neurofilament, heavy polypeptide 200kDa
|-
| ||
CHEK2CHEK2 is the official symbol for the human gene CHK2 checkpoint homolog. It is located on the long arm of chromosome 22.-Function:The protein encoded by this gene, CHK2 a protein kinase that is activated in response to DNA damage and is involved in cell cycle arrest.In response to DNA damage and...
|| CHK2 checkpoint homolog (S. pombe)
|-
| || NF2|| neurofibromin 2 || bilateral
acoustic neuromaAn acoustic neuroma, correctly called a vestibular schwannoma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve ....
|-
| ||
SOX10Transcription factor SOX-10 is a protein that in humans is encoded by the SOX10 gene....
|| SRY (sex determining region Y)-box 10
|-
| ||
EP300E1A binding protein p300 also known as EP300 or p300 is a protein which in humans is encoded by the EP300 gene. This protein regulates the activity of many genes in tissues throughout the body...
|| E1A binding protein p300
|-
| ||
WNT7BProtein Wnt-7b is a protein that in humans is encoded by the WNT7B gene.-Further reading:...
|| Wingless-type MMTV integration site family, member 7B
|-
| ||
SHANK3SH3 and multiple ankyrin repeat domains 3, also known as SHANK3, is a human gene on chromosome 22.-Further reading:...
|| SH3 and multiple ankyrin repeat domains 3 ||
22q13 deletion syndrome22q13 Deletion Syndrome , also known as Phelan-McDermid Syndrome, is a genetic disorder caused by a microdeletion on chromosome 22. The deletion occurs at the terminal end of the chromosome at the location designated q13.3...
|}
Diseases & disorders
The following diseases are some of those related to genes on chromosome 22:
- Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis is a form of motor neuron disease. ALS, sometimes called Maladie de Charcot, is a progressive, fatal, neurodegenerative disease caused by the degeneration of motor neurons, the nerve cells in the central nervous system that control voluntary muscle movement...
- Breast cancer
Breast cancer is a cancer that starts in the breast, usually in the inner lining of the milk ducts or lobules. There are different types of breast cancer, with different stages , aggressiveness, and genetic makeup. With best treatment, 10-year disease-free survival varies from 98% to 10%...
- 22q11.2 deletion syndrome
22q11.2 deletion syndrome, also known as DiGeorge Syndrome, Velocardiofacial Syndrome, conotruncal anomaly face syndrome, Congenital Thymic Aplasia, Strong Syndrome, Thymic hypoplasia, and DiGeorge anomaly is a syndrome caused by the deletion of a small piece of chromosome 22...
- 22q13 deletion syndrome
22q13 Deletion Syndrome , also known as Phelan-McDermid Syndrome, is a genetic disorder caused by a microdeletion on chromosome 22. The deletion occurs at the terminal end of the chromosome at the location designated q13.3...
or Phelan-McDermid syndrome
- Li-Fraumeni syndrome
Li-Fraumeni syndrome is a rare autosomal dominant hereditary disorder. It is named after Frederick Pei Li and Joseph F. Fraumeni, Jr., the American physicians who first recognized and described the syndrome. Li-Fraumeni syndrome increases greatly the susceptibility to cancer...
- Neurofibromatosis type 2
- Rubinstein-Taybi syndrome
Rubinstein-Taybi Syndrome Rubinstein-Taybi Syndrome Rubinstein-Taybi Syndrome (RTS; also known as Broad Thumb-Hallux syndrome is a condition characterized by short stature, moderate to severe learning difficulties, distinctive facial features, and broad thumbs and first toes. Other features of the...
- Waardenburg syndrome
Waardenburg syndrome or Waardenburg-Klein syndrome is a rare genetic disorder most often characterized by varying degrees of deafness, minor defects in structures arising from the neural crest, and pigmentation anomalies.-Eponyms and classification:...
- Cat eye syndrome
Cat Eye Syndrome is a very rare malformation involving Chromosome 22. The short arm and a small section of the long arm are present three or four times instead of the usual two times...
- Methemoglobinemia
Methemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is a form of hemoglobin that does not bind oxygen. When its concentration is elevated in red blood cells, tissue hypoxia can occur.-Overview:Normally,...
- Schizophrenia
Schizophrenia , from the Greek roots skhizein and phrēn, phren- is a psychiatric diagnosis that describes a mental disorder characterized by abnormalities in the perception or expression of reality...
Chromosomal conditions
The following conditions are caused by changes in the structure or number of copies of chromosome 22:
- 22q11.2 deletion syndrome
22q11.2 deletion syndrome, also known as DiGeorge Syndrome, Velocardiofacial Syndrome, conotruncal anomaly face syndrome, Congenital Thymic Aplasia, Strong Syndrome, Thymic hypoplasia, and DiGeorge anomaly is a syndrome caused by the deletion of a small piece of chromosome 22...
: Most people with 22q11.2 deletion syndrome are missing about 3 million base pairs on one copy of chromosome 22 in each cell. The deletion occurs near the middle of the chromosome at a location designated as q11.2. This region contains about 30 genes, but many of these genes have not been well characterized. A small percentage of affected individuals have shorter deletions in the same region.
The loss of one particular gene, TBX1, is thought to be responsible for many of the characteristic features of 22q11.2 deletion syndrome, such as heart defects, an opening in the roof of the mouth (a cleft palate), distinctive facial features, and low calcium levels. A loss of this gene does not appear to cause learning disabilities, however. Other genes in the deleted region are also likely to contribute to the signs and symptoms of 22q11.2 deletion syndrome.
- 22q13 deletion syndrome
22q13 Deletion Syndrome , also known as Phelan-McDermid Syndrome, is a genetic disorder caused by a microdeletion on chromosome 22. The deletion occurs at the terminal end of the chromosome at the location designated q13.3...
(Phelan-McDermid syndrome): The deletion of the distal tip of the chromosome 22 is related to moderate to severe developmental delay and mental retardation. This region includes the Shank3 gene, thought to be responsible for the neurological deficits of the syndrome (Wilson et al., 2003).
Almost all children affected by the 22q13 deletion have absent or severely delayed speech; minor facial dysmorphism; thin, flaky toenails; large, fleshy hands; large feet; prominent, poorly formed ears and other characteristics which are not visually apparent: hypotonia (97%); normal to accelerated growth (95%); increased tolerance to pain (86%); seizures (unknown percentage) http://www.22q13.org.
- Other chromosomal conditions: Other changes in the number or structure of chromosome 22 can have a variety of effects, including mental retardation, delayed development, physical abnormalities, and other medical problems. These changes include an extra piece of chromosome 22 in each cell (partial trisomy), a missing segment of the chromosome in each cell (partial monosomy), and a circular structure called ring chromosome 22 that is caused by the breakage and reattachment of both ends of the chromosome.
- Cat-eye syndrome is a rare disorder most often caused by a chromosomal change called an inverted duplicated 22. A small extra chromosome is made up of genetic material from chromosome 22 that has been abnormally duplicated (copied). The extra genetic material causes the characteristic signs and symptoms of cat-eye syndrome, including an eye abnormality called ocular iris coloboma (a gap or split in the colored part of the eye), small skin tags or pits in front of the ear, heart defects, kidney problems, and, in some cases, delayed development.
- A rearrangement (translocation
In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A fusion gene may be created when the translocation joins two otherwise separated genes, an event which is common in cancer. It is detected on cytogenetics or a...
) of genetic material between chromosomes 9 and 22 is associated with several types of blood cancer (leukemiaLeukemia is a cancer of the blood or bone marrow and is characterized by an abnormal proliferation of blood cells, usually white blood cells . Leukemia is a broad term covering a spectrum of diseases...
). This chromosomal abnormality, which is commonly called the Philadelphia chromosomePhiladelphia chromosome or Philadelphia translocation is a specific chromosomal abnormality that is associated with chronic myelogenous leukemia . It is the result of a reciprocal translocation between chromosome 9 and 22, and is specifically designated t...
, is found only in cancer cells. The Philadelphia chromosome has been identified in most cases of a slowly progressing form of blood cancer called chronic myeloid leukemia, or CML. It also has been found in some cases of more rapidly progressing blood cancers (acute leukemias). The presence of the Philadelphia chromosome can help predict how the cancer will progress and provides a target for molecular therapies.