Anagnou N P, Antonarakis S E, O'Brien S J, Modi W S, Nienhuis A W
Clinical Hematology Branch, National Heart, Lung and Blood Institute, Bethesda, MD 20205.
Am J Hum Genet. 1988 Feb;42(2):345-52.
The human dihydrofolate reductase (DHFR) gene family comprises one functional gene and at least four intronless processed pseudogenes. The functional DHFR gene is on chromosome 5, and DHFRP4 is on chromosome 3. Using in situ hybridization, we have now localized the functional DHFR gene to the region q11.1-q13.3 on chromosome 5. By genomic DNA analysis of a panel of human X rodent somatic-cell hybrids, we determined the chromosomal assignment of the DHFRP1 pseudogene to chromosome 18 and that of the DHFRP2 pseudogene to chromosome 6. The DHFRP1 pseudogene exhibits a novel form of polymorphism in humans in that it is present in the DNA of some individuals and absent in that of others. We investigated the racial distribution of this pseudogene in five racial groups. The allelic frequency as defined by analysis of 180 chromosomes was found to be 94% in Mediterraneans, 77% in Asian Indians, 67% in Chinese, 57% in Southeast Asians, and 32% in American blacks. These data suggest that the transposition of this "perfect" pseudogene occurred prior to the inception of the human racial groups.
人类二氢叶酸还原酶（DHFR）基因家族由一个功能基因和至少四个无内含子的加工假基因组成。功能性DHFR基因位于5号染色体上，而DHFRP4位于3号染色体上。通过原位杂交，我们现已将功能性DHFR基因定位到5号染色体上的q11.1-q13.3区域。通过对一组人类X啮齿动物体细胞杂种的基因组DNA分析，我们确定了DHFRP1假基因在18号染色体上的染色体定位以及DHFRP2假基因在6号染色体上的染色体定位。DHFRP1假基因在人类中表现出一种新的多态性形式，即它存在于一些个体的DNA中，而在另一些个体的DNA中不存在。我们研究了这个假基因在五个种族群体中的种族分布。通过对180条染色体的分析确定的等位基因频率在地中海人中为94%，在亚洲印度人中为77%，在中国人为67%，在东南亚人为57%，在美国黑人为32%。这些数据表明，这个“完美”假基因的转座发生在人类种族群体形成之前。
