Department of Biology, University of Utah, Salt Lake City, Utah 84112.
Genetics. 1980 Mar;94(3):733-48. doi: 10.1093/genetics/94.3.733.
Previous studies on linkage disequilibrium involving four tightly linked genes that code for the alpha-esterases of Drosophila montana suggest that these loci arose from a primitive esterase gene by gene duplication, followed by tandem duplication (Roberts and Baker 1973). We have examined the esterase variants in the closely related species, lacicola, flavomontana and borealis. These studies reveal that borealis has only a single esterase locus, and flavomontana may have only two loci. Cytological studies, using aceto-orcein staining and Hoechst fluorescence of squashes of ganglion chromosomes, reveal acrocentric Y chromosomes for all six species of the montana phylad, with the exception of borealis, which has the primitive rod-shaped Y chromosome. These studies provide evidence against the hypothesis (Stone, Guest and Wilson 1960) that borealis and flavomontana are derived from montana, but support Throckmorton's (1978) conclusion of the early divergence of the former two species. This phylogenetic relationship supports our contention that the difference in the number of esterase genes with active alleles between borealis and montana is based on an increase in the number of genes coding for the alpha-esterases, rather than the retention in borealis of three genes with null alleles.
先前关于涉及编码黑腹果蝇α-酯酶的四个紧密连锁基因的连锁不平衡的研究表明，这些基因座是由原始酯酶基因通过基因复制产生的，然后是串联重复（Roberts 和 Baker，1973）。我们已经研究了密切相关的物种lacicola、flavomontana 和 borealis 中的酯酶变体。这些研究表明，borealis 仅有一个单一的酯酶基因座，而 flavomontana 可能只有两个基因座。细胞学研究使用 aceto-orcein 染色和 ganglion 染色体压扁的 Hoechst 荧光，揭示了除了 borealis 之外，montana 科的所有六种物种都具有近端着丝粒的 Y 染色体，而 borealis 具有原始的杆状 Y 染色体。这些研究结果否定了 borealis 和 flavomontana 是从 montana 进化而来的假设（Stone、Guest 和 Wilson，1960），但支持了 Throckmorton（1978）关于前两种物种早期分化的结论。这种系统发育关系支持了我们的论点，即 borealis 和 montana 之间具有活性等位基因的酯酶基因数量的差异是基于编码α-酯酶的基因数量的增加，而不是 borealis 保留了三个具有无效等位基因的基因。
