Reston J T, Hu X L, Macina R A, Spais C, Riethman H C
Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
Genomics. 1995 Mar 1;26(1):31-8. doi: 10.1016/0888-7543(95)80079-2.
The most distal 300 kb of human chromosome 21q was cloned and mapped using telomeric yeast artificial chromosomes (YACs). The region contains low-copy subtelomeric repeats at the telomeric end, chromosome 21-specific sequences more centromerically, and the S100B gene at a distance of 100-140 kb from the chromosome terminus. RecA-assisted restriction endonuclease cleavage of genomic DNA showed that the cloned fragments correspond to telomere-terminal genomic DNA, and restriction enzyme mapping of the YACs shows that the smaller clone (175 kb) corresponds exactly to the telomeric end of the larger one (300 kb). PCR assays for 21q-specific markers were used to show that COL6A1, COL6A2, and LA161 were all outside of the subtelomeric region spanned by the YACs and thus at least 300 kb from the 21q terminus. The molecular probes provide telomeric closure for existing 21q maps.
使用端粒酵母人工染色体（YAC）克隆并定位了人类21号染色体长臂最远端的300 kb区域。该区域在端粒末端含有低拷贝亚端粒重复序列，在更靠近着丝粒的位置含有21号染色体特异性序列，以及距离染色体末端100 - 140 kb处的S100B基因。RecA辅助的基因组DNA限制性内切酶切割表明，克隆片段对应于端粒末端的基因组DNA，YAC的限制性酶切图谱显示较小的克隆（175 kb）与较大的克隆（300 kb）的端粒末端完全对应。用于21号染色体长臂特异性标记的PCR检测表明，COL6A1、COL6A2和LA161均在YAC跨越的亚端粒区域之外，因此距离21号染色体长臂末端至少300 kb。这些分子探针为现有的21号染色体长臂图谱提供了端粒封闭。
