الكروموسوم 22، هوواحد من 23 زوج من الكروموسومات البشرية. عادة ما يمتلك البشر زوجان من هذا الكروموسوم. الكروموسوم 22 هوثاني أصغر كروموسوم بشري (الكروموسوم 21 هوالأصغر)، يحتوي على حوالي 49 مليون زوج قاعدي (مادة بناء الدنا). ويمثل حوالي 1.5%-2% من إجمالي الدنا في الخلايا.

في 1991، أعرب الباحثون العاملون على مشروع الجينوم البشري عن تحديدهم لتسلسل الأزواج القاعدية الموجودة في هذا الكروموسوم. كان الكروموسوم 22 أول كرمومسوم بشري يتم تحديد تسلسله بالكامل.

نظراً لاختلاف المناهج التي يستخدمها الباحثون في التنبؤ بعدد الجينات في جميع كروموسوم، هناك تباين في أعداد الجينات المقدرة. من الأرجح حتى الكروموسوم 22 يحتوي على 693 جين.

يعهد الكرمومسوم 22 في الأصل على أنه أصغر كروموسوم بشري، لكن وبعد أبحاث موسعة، توصل الباحثون إلى حتى الكرومسوم 21 هوالأصغر. لم يعاد ترقيم هذه الكروموسومات لأن الكروموسوم 21 اشتهر بتعيينه ككروموسوم يمكن حتى يسبب متلازمة داون.

الجينات

الجدول التالي للجينات الموجودة على الكروموسوم 22:

الأمراض والاضطرابات

القائمة التالية لبعض الأمراض المرتبطة بالجينات الموجودة على الكروموسوم 22:

• Amyotrophic lateral sclerosis
• سرطان الثدي
• متلازمة ديجورون
• Desmoplastic small round cell tumor
• 22q11.2 deletion syndrome
• 22q11.2 distal deletion syndrome
• 22q13 deletion syndrome or Phelan-McDermid syndrome
• متلازمة لي-فراومني
• Neurofibromatosis type 2
• Rubinstein-Taybi syndrome
• Waardenburg syndrome
• متلازمة عين القط
• Methemoglobinemia
• انفصام الشخصية

الحالات الكروموسومية

القائمة التالية للحالات الطبية التي تسببها تغيرات في بنية أوعدد نسخ الكروموسوم 22:

• 22q11.2 deletion syndrome: Most people with 22q11.2 deletion syndrome are missing about ثلاثة 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.
• 22q11.2 distal deletion syndrome
• 22q13 deletion syndrome (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) [1].
• 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.
• متلازمة عين القط 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 chromosomesتسعة 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.
• Emanuel Syndrome is a translocation of chromosomes 11 and 22. Originally known as Supernumerary der(22) Syndrome, it occurs when an individual has an extra chromosome composed of pieces of the 11th and 22nd chromosomes.

المصادر

قراءات إضافية

• 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. doi:10.1038/990031. PMID 10591208.CS1 maint: multiple names: authors list (link)
• Gilbert F (1998). "Disease genes and chromosomes: disease maps of the human genome. Chromosome 22". Genet Test. 2 (1): 89–97. doi:10.1089/gte.1998.2.89. 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.CS1 maint: multiple names: authors list (link)
• 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. doi:10.1016/S0736-5748(02)00050-3. PMID 12175881.CS1 maint: multiple names: authors list (link)
• McDermid HE, Morrow BE (2002). "Genomic disorders on 22q11". Am J Hum Genet. 70 (5): 1077–88. doi:10.1086/340363. PMC 447586. 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.CS1 maint: multiple names: authors list (link)
• 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. doi:10.1101/gad.1055203. PMC 195998. PMID 12600945.CS1 maint: multiple names: authors list (link)
• Wilson HL, Wong ACC, Shaw SR, Tse WY, Stapleton GA, Phelan MC, Hu S, Marshall J, McDermid HE; et al. (2003). "Molecular characerisation of the 22q13 deletion syndrome supports the role of haploinsufficiency of SHANK3/PROSASP2 in the major neurological symptoms". J Med Genet. 40: 575–584. doi:10.1136/jmg.40.8.575. PMC 1735560. PMID 12920066. Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)