Chromosome 22 (human)
Encyclopedia
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 in human
Human
Humans are the only living species in the Homo genus...
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....
. Humans normally have two copies of Chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 49 million 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...
base pair
Base pair
In molecular biology and genetics, the linking between two nitrogenous bases on opposite complementary DNA or certain types of RNA strands that are connected via hydrogen bonds is called a base pair...
s and representing between 1.5 and 2 % of the total DNA in 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....
.
In 1999, researchers working on the Human Genome Project
Human Genome Project
The Human Genome Project is an international scientific research project with a primary goal of determining the sequence of chemical base pairs which make up DNA, and of identifying and mapping the approximately 20,000–25,000 genes of the human genome from both a physical and functional...
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 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
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@ 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 Light chain A light chain is the small polypeptide subunit of a protein complex.More specifically, it can refer to:* Immunoglobulin light chain* Ferritin light chain* Myosin light chain* Kinesin light chain* Dynein light chainLight chain may also refer to:... s of antibodies Antibody An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen... >- | |
TBX1 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... |
Reticulon 4 receptor
Reticulon 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...
|| Schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
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| || COMT|| catechol-O-methyltransferase gene
|-
| || NEFH
NEFH
NEFH is a human gene located on chromosome 22 that stands for "neurofilament, heavy polypeptide". It is the gene for a heavy protein subunit that is combined with medium and light subunits to make neurofilaments, which form the framework for nerve cells....
|| neurofilament, heavy polypeptide 200kDa
|-
| || CHEK2
CHEK2
CHEK2 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 neuroma
Acoustic neuroma
A vestibular schwannoma, often called an acoustic neuroma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve . The term "vestibular schwannoma" involves the vestibular portion of the 8th cranial nerve and arises from Schwann cells, which are...
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| || SOX10
SOX10
Transcription factor SOX-10 is a protein that in humans is encoded by the SOX10 gene....
|| SRY (sex determining region Y)-box 10
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| || EP300
EP300
E1A binding protein p300 also known as EP300 or p300 is a protein that, 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
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| || WNT7B
WNT7B
Protein Wnt-7b is a protein that in humans is encoded by the WNT7B gene.-Further reading:...
|| Wingless-type MMTV integration site family, member 7B
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| || SHANK3
SHANK3
SH3 and multiple ankyrin repeat domains 3, also known as SHANK3, is a human gene on chromosome 22.This gene is a member of the Shank gene family. Shank proteins are multidomain scaffold proteins of the postsynaptic density that connect neurotransmitter receptors, ion channels, and other membrane...
|| SH3 and multiple ankyrin repeat domains 3 || 22q13 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...
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Diseases & disorders
The following diseases are some of those related to genes on chromosome 22:- Amyotrophic lateral sclerosisAmyotrophic lateral sclerosisAmyotrophic lateral sclerosis , also referred to as Lou Gehrig's disease, is a form of motor neuron disease caused by the degeneration of upper and lower neurons, located in the ventral horn of the spinal cord and the cortical neurons that provide their efferent input...
- Breast cancerBreast cancerBreast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
- Desmoplastic small round cell tumorDesmoplastic small round cell tumorDesmoplastic small-round-cell tumor is classified as a soft tissue sarcoma. It is an aggressive and rare tumor that primarily occurs as masses in the abdomen. Other areas affected may include the lymph nodes, the lining of the abdomen, diaphragm, spleen, liver, chest wall, skull, spinal cord, large...
- 22q11.2 deletion syndrome
- 22q13 deletion syndrome22q13 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...
or Phelan-McDermid syndrome - Li-Fraumeni syndromeLi-Fraumeni syndromeLi-Fraumeni syndrome is an extremely 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 greatly increases susceptibility to cancer...
- Neurofibromatosis type 2
- Rubinstein-Taybi syndromeRubinstein-Taybi syndromeRubinstein-Taybi Syndrome , also known as broad thumb-hallux syndrome or Rubinstein 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 disorder vary among affected...
- Waardenburg syndromeWaardenburg syndromeWaardenburg syndrome Waardenburg syndrome Waardenburg syndrome (also Waardenburg Shah Syndrome, Waardenburg-Klein syndrome, Mende's syndrome II, Van der Hoeve-Halbertsma-Waardenburg syndrome, Ptosis-Epicanthus syndrome, Van der Hoeve-Halbertsma-Gualdi syndrome, Waardenburg type Pierpont,[5] Van...
- Cat eye syndromeCat eye syndromeCat Eye Syndrome is a rare condition caused by the short arm and a small section of the long arm of human Chromosome 22 being present three or four times instead of the usual two times. The term "Cat Eye" syndrome was coined because of the particular appearance of the vertical colobomas in the...
- MethemoglobinemiaMethemoglobinemiaMethemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has an increased affinity for oxygen, resulting in a reduced ability to release oxygen to tissues. The oxygen–hemoglobin...
- SchizophreniaSchizophreniaSchizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
Chromosomal conditions
The following conditions are caused by changes in the structure or number of copies of chromosome 22:- 22q11.2 deletion syndrome: 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 syndrome22q13 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...
(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 (translocationChromosomal translocationIn genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer. It is detected on...
) of genetic material between chromosomes 9 and 22 is associated with several types of blood cancer (leukemiaLeukemiaLeukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...
). This chromosomal abnormality, which is commonly called the Philadelphia chromosomePhiladelphia 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.