POPULATION GENETICS OF TRANSPOSABLE ELEMENTS

现在有一个完善的定量理论体系， 有性物种转座因子的群体遗传学。 这 理论预测，在染色体位点的元素频率， 元素在自然种群中的含量应该很低。 如果selection 限制拷贝数，X连锁位点的频率将降低 而不是常染色体位点。 此外，将有一种趋势， 在基因组区域中优先积累的元件， 在缺席。 建议在果蝇中测试这些预测，使用 标记探针原位杂交技术， 多线唾液染色体的重复DNA。 元素积累 将通过测定 的元素在旧的建立，实验室平衡反演股票， 罕见的自然发生的倒位，并在地区的交叉是 通常不存在，如染色体4和X的远端。 将与适当对照中的丰度进行比较。 样品 自然群体的X、2、3、4号染色体将用于 检查低元素频率和低丰度的预测 X上的元素相对于常染色体。

There is now a well-established body of quantitative theory concerning the population genetics of transposable elements in sexual species. This theory predicts that element frequencies at chromosomal sites into which elements can insert should be low in natural populations. If selection acts to limit copy numbers, frequencies at X-linked sites will be lower than at autosomal sites. Furthermore, there will be a tendency for elements to accumulate preferentially in genomic regions where crossing over is absent. It is proposed to test these predictions in Drosophila melanogaster, using the technique of in situ hybridization of labeled probes of families of repeated DNA to polytene salivary chromosomes. Accumulation of elements with restricted crossing over will be tested by determining the abundance of elements in old-established, laboratory balanced inversion stocks, in rare naturally occurring inversions, and in regions where crossing over is normally absent such as chromosome 4 and the distal end of the X. Comparisons will be made with the abundance in suitable controls. Samples of X, 2nd, 3rd and 4th chromosomes from natural populations will be used to check the predictions of low element frequencies and a lower abundance of elements on the X relative to the autosomes.