Department of Zoology and Genetics Program, Colleges of Natural Science and Osteopath'c Medicine, Michigan State University, East Lansing, Michigan 48824.
Genetics. 1980 Feb;94(2):361-81. doi: 10.1093/genetics/94.2.361.
Heterozygosity for a deficiency for the entire zeste-white region of the X chromosome of Drosophila melanogaster females causes both reduced recombination and increased nondisjunction. The location of the dosage-sensitive sites responsible for these two meiotic defects has been studied by use of a set of deficiencies that subdivide the region. Recombination is reduced when the zw7-zw11 region is present in one dose, while nondisjunction is increased only if the doses of both the zw8-zw10 and zw6-zw11 segments are reduced. Examination of trans heterozygotes of two deficiencies explicitly demonstrates the compound nature of the meiotic dose effect and further delimits the location of the proximal disjunctional site to the zw12-zw11 interval. In inversion/deficiency heterozygotes, reduced dose of the zw8-zw10 region alone, without reduced dose of the proximal site, yields increased nondisjunction, suggesting that the proximal element that affects disjunction is the same as that which affects recombination. Thus, the zeste-white region contains at least two dosagesensitive loci that affect meiosis: reduced dosage of one locus, in the zw7-zw11 interval, causes reduced recombination; reduced dose of another, in the zw8-zw10 region, increases the probability that nonexchange chromosomes will nondisjoin. A slight effect on the regional distribution of exchange may also be a property of the zw8-zw10 region locus, but could be an effect of yet another locus or of structural heterozygosity. The implications of these results for understanding meiotic control and the prospects for further analysis of the structure of the zeste-white interval are considered.
果蝇雌性个体 X 染色体的整个 zeste-white 区域的杂合子缺失会导致重组减少和非姊妹染色单体分离增加。通过使用一组细分该区域的缺失来研究负责这两种减数分裂缺陷的剂量敏感位点的位置。当存在一个剂量的 zw7-zw11 区域时，重组减少，而只有当 zw8-zw10 和 zw6-zw11 片段的剂量都降低时，非姊妹染色单体分离才会增加。对两个缺失的 trans 杂合体的检查明确表明了减数分裂剂量效应的复合性质，并进一步将近端分离位点的位置限定在 zw12-zw11 区间内。在倒位/缺失杂合体中，仅 zw8-zw10 区域的剂量减少，而近端位点的剂量不减，导致非姊妹染色单体分离增加，这表明影响分离的近端元件与影响重组的元件相同。因此，zeste-white 区域至少包含两个影响减数分裂的剂量敏感位点：在 zw7-zw11 区间内的一个位点的剂量减少会导致重组减少；在 zw8-zw10 区域的另一个位点的剂量减少会增加无交换染色体非姊妹染色单体分离的概率。交换的区域分布也可能是 zw8-zw10 区域位点的一个轻微影响，但也可能是另一个位点或结构杂合性的影响。这些结果对理解减数分裂控制以及进一步分析 zeste-white 间隔结构的前景具有重要意义。
