Nuzhdin S V
Department of Genetics, North Carolina State University, Raleigh 27695-7614, USA.
Genet Res. 1995 Oct;66(2):159-66. doi: 10.1017/s0016672300034509.
The distribution of 13 transposable element families along 15 X chromosomes from an African natural population of Drosophila simulans was determined by in situ hybridization to polytene chromosomes. The transposable elements cloned from Drosophila melanogaster all hybridized with Drosophila simulans chromosomes. The number of copies per family was 3.5 times lower in the latter species and correlated with the copy number per family in Drosophila melanogaster. With the exception of 297, the copy number per chromosome followed a Poisson distribution. Element frequencies per chromosome band were generally low. However, several sites of the distal region and the base of the X chromosome had high frequencies of occupation. Elements had higher abundance at the base of the chromosome compared to distal regions. Overall, the distribution of transposable elements in Drosophila simulans is similar to that found in Drosophila melanogaster. These data provide evidence for the operation of a force (or forces) opposing transpositional increase in copy number, and that this force is weaker at the bases of chromosomes, consistent with the idea that recombination between elements at non-homologous sites contains TE copy number. The reduction in copy number of all TE families in Drosophila simulans compared to Drosophila melanogaster can be explained by stronger selection against transposable element multiplication and/or lower rates of transposition in Drosophila simulans.
通过对多线染色体进行原位杂交，确定了来自非洲黑腹果蝇自然种群的15条X染色体上13个转座元件家族的分布情况。从黑腹果蝇中克隆的转座元件均能与黑腹果蝇的染色体杂交。在后者物种中，每个家族的拷贝数低3.5倍，并且与黑腹果蝇中每个家族的拷贝数相关。除297外，每条染色体的拷贝数遵循泊松分布。每条染色体带的元件频率通常较低。然而，X染色体远端区域和基部的几个位点具有较高的占据频率。与远端区域相比，元件在染色体基部的丰度更高。总体而言，黑腹果蝇中转座元件的分布与黑腹果蝇中的相似。这些数据为存在一种（或多种）对抗拷贝数转座增加的力量提供了证据，并且这种力量在染色体基部较弱，这与非同源位点元件之间的重组控制转座元件拷贝数的观点一致。与黑腹果蝇相比，黑腹果蝇中所有转座元件家族拷贝数的减少可以通过对转座元件增殖的更强选择和/或黑腹果蝇中转座率较低来解释。
