Golic M M, Golic K G
Department of Biology, University of Utah, Salt Lake City 84112, USA.
Genetics. 1996 May;143(1):385-400. doi: 10.1093/genetics/143.1.385.
In Drosophila there exist several examples of gene expression that can be modified by an interaction between alleles; this effect is known as transvection. The inference that alleles interact comes from the observations that homologous chromosomes pair in mitotically dividing cells, and that chromosome rearrangements can alter the phenotype produced by a pair of alleles. It is thought that heterozygous rearrangements impede the ability of alleles to pair and interact. However, because the existing data are inconsistent, this issue is not fully settled. By measuring the frequency of site-specific recombination between homologous chromosomes, we show that structural heterozygosity inhibits the pairing of alleles that lie distal to a rearrangement breakpoint. We suggest that some of the apparent conflicts may owe to variations in cell-cycle lengths in the tissues where the relevant allelic interactions occur. Cells with a longer cell cycle have more time to establish the normal pairing relationships that have been disturbed by rearrangements. In support, we show that Minute mutations, which slow the rate of cell division, partially restore a transvection effect that is disrupted by inversion heterozygosity.
在果蝇中，存在几个基因表达的例子，其可通过等位基因之间的相互作用而被改变；这种效应被称为异位效应。等位基因相互作用的推断源于以下观察结果：同源染色体在有丝分裂的细胞中配对，并且染色体重排可改变由一对等位基因产生的表型。据认为，杂合染色体重排会妨碍等位基因配对和相互作用的能力。然而，由于现有数据不一致，这个问题尚未完全解决。通过测量同源染色体之间位点特异性重组的频率，我们表明结构杂合性会抑制位于重排断点远端的等位基因的配对。我们认为，一些明显的冲突可能归因于相关等位基因相互作用发生的组织中细胞周期长度的变化。细胞周期较长的细胞有更多时间来建立因重排而受到干扰的正常配对关系。作为支持，我们表明，减慢细胞分裂速率的微小突变可部分恢复因倒位杂合性而被破坏的异位效应。
