Young M W
Proc Natl Acad Sci U S A. 1979 Dec;76(12):6274-8. doi: 10.1073/pnas.76.12.6274.
Most of the middle repetitive DNA of Drosophila melanogaster appears to be organized into families of 10-100 repeated elements that are found at scattered locations in the chromosome arms and occupy new chromosomal positions as populations of D. melanogaster diverge. These "nomadic" DNA segments can be identified by an analysis of cDm plasmids, hybrids of ColE1 and segments of randomly sheared D. melanogaster DNA. Eighty cDm plasmids were withdrawn, at random, from a library of approximately 17,000 cDm clones. Fifty-seven of these seem to contain either DNA that is not repeated in the D. melanogaster genome or DNA that has a low repetition frequency. The remaining 23 cDm plasmids contain repetitive sequences. Seventeen of these 23 plasmids contain repetitive sequences that are demonstrably scattered to many chromosomal sites that can be mapped in two D. melanogaster strains, g-1 and g-X11. The repeated elements hybridizing with each of the different Dm segments are at quite different chromosomal locations in these two strains. However, the size of each family of repeated sequences remains fairly constant in both strains. It is proposed that the number of elements in each family has been fixed by selection.
黑腹果蝇的大多数中度重复DNA似乎被组织成由10 - 100个重复元件组成的家族，这些元件分布在染色体臂的分散位置，并且随着黑腹果蝇种群的分化而占据新的染色体位置。这些“游牧”DNA片段可以通过对cDm质粒（ColE1与随机剪切的黑腹果蝇DNA片段的杂交体）的分析来鉴定。从大约17000个cDm克隆的文库中随机抽取了80个cDm质粒。其中57个似乎含有在黑腹果蝇基因组中不重复的DNA或重复频率低的DNA。其余23个cDm质粒含有重复序列。这23个质粒中的17个含有可明显分散到许多染色体位点的重复序列，这些位点可在两种黑腹果蝇品系g - 1和g - X11中进行定位。与每个不同Dm片段杂交的重复元件在这两个品系中的染色体位置截然不同。然而，两个品系中每个重复序列家族的大小保持相当恒定。有人提出每个家族中的元件数量已通过选择固定下来。
