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Encyclopedia > Chromosome 22 (human)

Chromosome 22 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 22 is the second smallest human chromosome, spanning about 49 million base pairs (the building material of DNA) and representing between 1.5 and 2 percent of the total DNA in cells. Figure 1: Chromosome. ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu(extinct) Homo sapiens sapiens Homo (genus). ... In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and most viruses). ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ...


In 1999, researchers working on the Human Genome Project 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. 1999 (MCMXCIX) is a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... The Human Genome Project (HGP) endeavored to map the human genome down to the nucleotide (or base pair) level and to identify all the genes present in it. ...


Identifying genes 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 likely contains between 500 and 800 genes. This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ...

Contents


Genes

The following are some of the genes located on chromosome 22:

  • CHEK2: CHK2 checkpoint homolog (S. pombe)
  • EP300: E1A binding protein p300
  • NEFH: neurofilament, heavy polypeptide 200kDa
  • NF2: neurofibromin 2 (bilateral acoustic neuroma)
  • SOX10: SRY (sex determining region Y)-box 10
  • TBX1: T-box 1

In medicine, the neurofibromatoses (singular, neurofibromatosis) are certain genetic disorders of the nervous system. ...

Diseases

The following diseases are some of those related to genes on chromosome 22:

Motor Neurone Disease (MND) is a term used to cover a number of illnesses of the motor neurone. ... Breast cancer is cancer of breast tissue. ... Li-Fraumeni syndrome is a rare autosomal dominant hereditary disorder. ... In medicine, the neurofibromatoses (singular, neurofibromatosis) are certain genetic disorders of the nervous system. ... Rubinstein-Taybi syndrome (also known as Broad Thumb-Hallux syndrome) is a condition characterized by short stature, moderate to severe mental retardation, distinctive facial features, and broad thumbs and first toes. ... Waardenburg syndrome is an inherited disorder associated with hearing loss and changes in skin and hair pigmentation. ...

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.

  • 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) of genetic material between chromosomes 9 and 22 is associated with several types of blood cancer (leukemia). This chromosomal abnormality, which is commonly called the Philadelphia chromosome, 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.

Chromosomal translocation of the 4th and 20th chromosome. ... Leukemia (leukaemia in Commonwealth English) is a cancer of the blood or bone marrow characterized by an abnormal proliferation of white blood cells (leukocytes). ... Philadelphia chromosome or Philadelphia translocation is a specific genetic, chromosomal abnormality that is associated with chronic myelogenous leukemia (CML) and involves an exchange of material between chromosomes 9 and 22. ...

References

  • Dunham I, Shimizu N, Roe BA, Chissoe S, Hunt AR, Collins JE, Bruskiewich R, Beare DM, Clamp M, Smink LJ, Ainscough R, Almeida JP, Babbage A, Bagguley C, Bailey J, Barlow K, Bates KN, Beasley O, Bird CP, Blakey S, Bridgeman AM, Buck D, Burgess J, Burrill WD, O'Brien KP (1999). The DNA sequence of human chromosome 22. Nature 402 (6761): 489-95. PMID 10591208
  • Gilbert F (1998). Disease genes and chromosomes: disease maps of the human genome. Chromosome 22. Genet Test 2 (1): 89-97. PMID 10464604
  • Kurzrock R, Kantarjian HM, Druker BJ, Talpaz M (2003). Philadelphia chromosome-positive leukemias: from basic mechanisms to molecular therapeutics. Ann Intern Med 138 (10): 819-30. PMID 12755554
  • Maynard TM, Haskell GT, Lieberman JA, LaMantia AS (2002). 22q11 DS: genomic mechanisms and gene function in DiGeorge/velocardiofacial syndrome. Int J Dev Neurosci 20 (3-5): 407-19. PMID 12175881
  • McDermid HE, Morrow BE (2002). Genomic disorders on 22q11. Am J Hum Genet 70 (5): 1077-88. PMID 11925570
  • McDonald-McGinn DM, Kirschner R, Goldmuntz E, Sullivan K, Eicher P, Gerdes M, Moss E, Solot C, Wang P, Jacobs I, Handler S, Knightly C, Heher K, Wilson M, Ming JE, Grace K, Driscoll D, Pasquariello P, Randall P, Larossa D, Emanuel BS, Zackai EH (1999). The Philadelphia story: the 22q11.2 deletion: report on 250 patients. Genet Couns 10 (1): 11-24. PMID 10191425
  • Rinn JL, Euskirchen G, Bertone P, Martone R, Luscombe NM, Hartman S, Harrison PM, Nelson FK, Miller P, Gerstein M, Weissman S, Snyder M (2003). The transcriptional activity of human Chromosome 22. Genes Dev 17 (4): 529-40. PMID 12600945
Human chromosomes edit

{1} {2} {3} {4} {5} {6} {7} {8} {9} {10} {11} {12} {13} {14} {15} {16} {17} {18} {19} {20} {21} {22} {X} {Y} Figure 1: Chromosome. ... Chromosome 1 is one of the 23 pairs of chromosomes in humans. ... Chromosome 10 is one of the 23 pairs of chromosomes in humans. ... Chromosome 11 is one of the 23 pairs of chromosomes in humans. ... Chromosome 12 is one of the 23 pairs of chromosomes in humans. ... Chromosome 13 is one of the 23 pairs of chromosomes in humans. ... Chromosome 14 is one of the 23 pairs of chromosomes in humans. ... Chromosome 15 is one of the 23 pairs of chromosomes in humans. ... Chromosome 16 is one of the 23 pairs of chromosomes in humans. ... Chromosome 17 is one of the 23 pairs of chromosomes in humans. ... Chromosome 18 is one of the 23 pairs of chromosomes in humans. ... Chromosome 19 is one of the 23 pairs of chromosomes in humans. ... Chromosome 20 is one of the 23 pairs of chromosomes in humans. ... A common disease due to 3 of such chromosomes instead of the normal 2 is called Down syndrome. ... The human X chromosome, is is one of the two chromosomes involved in the XY sex-determination system. ... The human Y chromosome is one of two sex chromosomes, it contains the genes that cause testis development, thus determining maleness. ...


  Results from FactBites:
 
NIH News Release: Human Chromosome 22: First to be Decoded (1166 words)
Chromosome 22 is the first of 23 human chromosome pairs to be deciphered because of its relatively small size and its association with several diseases and because of the groundwork of several scientists beginning in the early 1990s.
Comparing the chromosome 22 sequence to known gene sequences of the mouse, a lab animal frequently used to facilitate understanding of human genetic disorders, the research team found 160 human genes that have comparable sequences in the mouse.
Examining the chromosomal locations of the mouse genes that have counterparts on the human chromosome 22 shows that the order of the genes along the chromosome in the two species is genetically conserved, although the mouse homologs of human genes on chromosome 22 are dispersed to eight different mouse chromosomal regions.
genome.gov | 1999 Release: First Human Chromosome Sequenced (1094 words)
Chromosome 22 is the first of 23 human chromosome pairs to be deciphered because of its relatively small size and its association with several diseases and because of the groundwork of several scientists beginning in the early 1990s.
Comparing the chromosome 22 sequence to known gene sequences of the mouse, a lab animal frequently used to facilitate understanding of human genetic disorders, the research team found 160 human genes that have comparable sequences in the mouse.
Examining the chromosomal locations of the mouse genes that have counterparts on the human chromosome 22 shows that the order of the genes along the chromosome in the two species is genetically conserved, although the mouse homologs of human genes on chromosome 22 are dispersed to eight different mouse chromosomal regions.
  More results at FactBites »

 
 

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