Fischel-Ghodsian N, Nicholls R D, Higgs D R
Nucleic Acids Res. 1987 Aug 11;15(15):6197-207. doi: 10.1093/nar/15.15.6197.
A map encompassing 300 kilobases (kb) in and around the human alpha-globin gene complex shows features with important implications for understanding the structure and function of the human genome. In contrast to other segments of the mammalian genome that have been analysed by pulsed field gradient electrophoresis (PFGE), this region contains an unusually high density of sites for infrequently cutting restriction enzymes that recognise GC rich motifs including the under-represented CpG doublet. This suggests that the 26 kilobase (kb) stretch of DNA containing the alpha-globin gene family, which is known from sequence analysis to be 60% GC rich, is itself embedded within a region of high GC content. This long-range structure, identified by PFGE, corresponds to a class of GC rich isochores that are thought to represent early replicating DNA present in Giemsa negative chromosomal bands. The identification of such regions by PFGE will be of value in understanding the organisation of human chromosomes and will influence the strategies used to construct a physical map of the genome.
一幅涵盖人类α-珠蛋白基因复合体及其周边300千碱基（kb）的图谱显示出了一些特征，这些特征对于理解人类基因组的结构和功能具有重要意义。与通过脉冲场梯度电泳（PFGE）分析的哺乳动物基因组的其他片段不同，该区域含有异常高密度的稀有切割限制酶位点，这些酶识别富含GC的基序，包括含量较低的CpG双联体。这表明，从序列分析已知富含60% GC的包含α-珠蛋白基因家族的26千碱基（kb）DNA片段本身就嵌入在一个高GC含量的区域内。通过PFGE鉴定的这种长程结构对应于一类富含GC的等密度区带，据认为它们代表了吉姆萨阴性染色体带中存在的早期复制DNA。通过PFGE鉴定此类区域对于理解人类染色体的组织将具有重要价值，并将影响构建基因组物理图谱所采用的策略。
