Molecular cytogenetic study of species-specific chromosomal regions

随着人类基因组草图序列的披露和公布，这一研究领域遇到了一个新的阶段。人类基因组组成的基因功能和生物学意义可能是进一步研究的主题。在本研究中，我们尝试寻找物种特有的染色体区域。在本研究中，人们的兴趣主要集中在人类2号染色体的进化融合点上。人们已经知道，人类2号染色体起源于两个祖先灵长类染色体的融合。染色体显带和与人类2号染色体特异DNA文库的荧光原位杂交(FISH)证实了这一点。本研究利用人2号染色体及其同源染色体的高分辨率FISH技术，准确测定了人类染色体2Q12-Q14区38个粘粒克隆在黑猩猩(Pantrogrodyzdes，2n=48)和食蟹猴(Macaca Fascular aris，2n=42)中的序列。该区域包括两个祖先类人猿类型染色体的端粒到端粒融合点。通过与黑猩猩和食蟹猴染色体的比较，发现人类染色体2Q12-Q14区对应于黑猩猩12和13号染色体的短臂，与食蟹猴9号和15号染色体的短臂相对应。这表明，两个祖先类人猿类型的染色体在端粒上完全融合形成了人类第二染色体，该区域的基因组组织被认为是相当保守的。然而，在食蟹猴身上，每个同源基因中克隆的顺序是颠倒的。有趣的是，融合点周围重复排列的数量显示出多态。

Since the draft sequences of the human genome were disclosed and publicized, this research field encounters a new phase. Gene function and biological significance of the constitution of human genome may be the main theme for further investigation. In the present study, search for the species-specific chromosomal regions has been attempted. In the present study, interests were focused on the evolutionary fusion point of human chromosome 2.It has been known that human chromosome 2 originated from the fusion of two ancestral primate chromosomes. This has been confirmed by chromosome banding and fluorescence in situ hybridization (FISH) with human chromosome-2-specific DNA libraries. In this study, the order of 38 cosmid clones derived from the human chromosome region 2q12-q14 was exactly determined by high-resolution FISH in human chromosome 2 and its homologous chromosomes in chimpanzees (Pan trogrodyzdes, 2n=48) and cynomolgus monkeys (Macaca fascicularis, 2n=42). This region includes the telomere-to-telomere fusion point of two ancestral ape-type chromosomes. As a result of comparisons with chimpanzee and cynomolgus monkey chromosomes, human chromosome region 2q12-q14 was found to correspond to the short arms of chimpanzee chromosomes 12 and 13 and cynomolgus monkey chromosomes 9 and 15. It is noted that no difference was detected in the relative order of the cosmid clones between human and chimpanzee chromosomes. This suggests that two ancestral ape-type chromosomes fused tandemly at telomeres to form human chromosome 2, and the genomic organization of this region is thought to be considerably conserved. In the cynomolgus monkey, however, the order of clones in each homologue was inverted. Interestingly, the number of repeated arrays around the fusion point was found to exhibit polymorphism.