Simpson N E
Department of Paediatrics, Queen's University, Kingston, Ontario, Canada.
J Med Genet. 1988 Dec;25(12):794-804. doi: 10.1136/jmg.25.12.794.
The number of gene assignments to human chromosome 20 has increased slowly until recently. Only seven genes and one fragile site were confirmed assignments to chromosome 20 at the Ninth Human Gene Mapping Workshop in September 1987 (HGM9). One fragile site, 13 additional genes, and 10 DNA sequences that identify restriction fragment length polymorphisms (RFLPs), however, were provisionally added to the map at HGM9. Five mutated genes on chromosome 20 have a relation to disease: a mutation in the adenosine deaminase gene results in a deficiency of the enzyme and severe combined immune deficiency; mutations in the gene for the growth hormone releasing factor result in some forms of dwarfism; mutations in the closely linked genes for the hormones arginine vasopressin and oxytocin and their neurophysins are probably responsible for some diabetes insipidus; and mutations in the gene that regulates both alpha-neuraminidase and beta-galactosidase activities determine galactosialidosis. The gene for the prion protein is on chromosome 20; it is related to the infectious agent of kuru, Creutzfeld-Jacob disease, and Gertsmann-Straussler syndrome, although the nature of the relationship is not completely understood. Two genes that code for tyrosine kinases are on the chromosome, SRC1 the proto-oncogene and a gene (HCK) coding for haemopoietic kinase (an src-like kinase), but no direct relation to cancer has been shown for either of these kinases. The significance of non-random loss of chromosome 20 in the malignant diseases non-lymphocytic leukaemia and polycythaemia vera is not understood. Twenty-four additional loci are assigned to the chromosome: five genes that code for binding proteins, one for a light chain of ferritin, genes for three enzymes (inosine triphosphatase, s-adenosylhomocysteine hydrolase, and sterol delta 24-reductase), one for each of a secretory protein and an opiate neuropeptide, a cell surface antigen, two fragile sites, and 10 DNA sequences (one satellite and nine unique) that detect RFLPs.
直到最近，定位到人类20号染色体上的基因数量增长缓慢。在1987年9月召开的第九届人类基因定位研讨会（HGM9）上，仅有7个基因和1个脆性位点被确认为定位于20号染色体。然而，在HGM9会议上，又临时将1个脆性位点、另外13个基因以及10个可识别限制性片段长度多态性（RFLP）的DNA序列添加到了图谱中。20号染色体上有5个突变基因与疾病相关：腺苷脱氨酶基因突变会导致该酶缺乏以及严重联合免疫缺陷；生长激素释放因子基因突变会引发某些类型的侏儒症；与激素精氨酸加压素和催产素及其神经垂体素紧密连锁的基因发生突变，可能是某些尿崩症的病因；而同时调节α-神经氨酸酶和β-半乳糖苷酶活性的基因突变则决定了半乳糖唾液酸贮积症。朊病毒蛋白基因位于20号染色体上；它与库鲁病、克雅氏病和格斯特曼-施特劳斯勒综合征的病原体有关，尽管它们之间关系的本质尚未完全明确。染色体上有两个编码酪氨酸激酶的基因，原癌基因SRC1和一个编码造血激酶（一种src样激酶）的基因（HCK），但尚未发现这两种激酶中的任何一种与癌症有直接关联。在非淋巴细胞白血病和真性红细胞增多症等恶性疾病中，20号染色体非随机丢失的意义尚不清楚。另外还有24个基因座被定位到该染色体上：5个编码结合蛋白的基因、1个铁蛋白轻链基因、3种酶（肌苷三磷酸酶、S-腺苷同型半胱氨酸水解酶和甾醇δ24-还原酶）的基因、1个分泌蛋白基因和1个阿片类神经肽基因、1个细胞表面抗原基因、2个脆性位点以及10个可检测RFLP的DNA序列（1个卫星序列和9个单一序列）。
