Baker B S, Hoff G, Kaufman T C, Wolfner M F, Hazelrigg T
Biology Department, University of California, San Diego 92093.
Genetics. 1991 Jan;127(1):125-38. doi: 10.1093/genetics/127.1.125.
The region of the third chromosome (84D-F) of Drosophila melanogaster that contains the doublesex (dsx) locus has been cytogenetically analyzed. Twenty nine newly induced, and 42 preexisting rearrangements broken in dsx and the regions flanking dsx have been cytologically and genetically characterized. These studies established that the dsx locus is in salivary chromosome band 84E1-2. In addition, these observations provide strong evidence that the dsx locus functions only to regulate sexual differentiation and does not encode a vital function. To obtain new alleles at the dsx locus and to begin to analyze the genes flanking dsx, 59 lethal and visible mutations in a region encompassing dsx were induced. These mutations together with preexisting mutations in the region were deficiency mapped and placed into complementation groups. Among the mutations we isolated, four new mutations affecting sexual differentiation were identified. All proved to be alleles of dsx, suggesting that dsx is the only gene in this region involved in regulating sexual differentiation. All but one of the new dsx alleles have equivalent effects in males and females. The exception, dsxEFH55, strongly affects female sexual differentiation, but only weakly affects male sexual differentiation. The interactions of dsxEFH55 with mutations in other genes affecting sexual differentiation are described. These results are discussed in terms of the recent molecular findings that the dsx locus encodes sex-specific proteins that share in common their amino termini but have different carboxyl termini. The 72 mutations in this region that do not affect sexual differentiation identify 25 complementation groups. A translocation, T(2;3)Es that is associated with a lethal allele in one of these complementation groups is also broken at the engrailed (en) locus on the second chromosome and has a dominant phenotype that may be due to the expression of en in the anterior portion of the abdominal tergites where en is not normally expressed. The essential genes found in the 84D-F region are not evenly distributed throughout this region; most strikingly the 84D1-11 region appears to be devoid of essential genes. It is suggested that the lack of essential genes in this region is due to the region (1) containing genes with nonessential functions and (2) being duplicated, possibly both internally and elsewhere in the genome.
对黑腹果蝇第三号染色体（84D - F）上包含双性基因（dsx）位点的区域进行了细胞遗传学分析。对29个新诱导产生的以及42个先前存在的、在dsx及其侧翼区域发生断裂的重排进行了细胞学和遗传学特征分析。这些研究确定dsx位点位于唾液腺染色体带84E1 - 2。此外，这些观察结果提供了有力证据，表明dsx位点仅起到调节性别分化的作用，并不编码重要功能。为了在dsx位点获得新的等位基因并开始分析dsx侧翼的基因，在包含dsx的区域诱导了59个致死和可见突变。将这些突变与该区域先前存在的突变一起进行缺失定位并归入互补群。在我们分离的突变中，鉴定出4个影响性别分化的新突变。所有这些突变都被证明是dsx的等位基因，这表明dsx是该区域唯一参与调节性别分化的基因。除了一个新的dsx等位基因外，其他所有等位基因在雄性和雌性中的作用相同。例外的是dsxEFH55，它强烈影响雌性性别分化，但对雄性性别分化的影响较弱。描述了dsxEFH55与其他影响性别分化的基因突变之间的相互作用。根据最近的分子研究结果对这些结果进行了讨论，即dsx位点编码性别特异性蛋白质，这些蛋白质的氨基末端相同但羧基末端不同。该区域中不影响性别分化的72个突变确定了25个互补群。一个易位T(2;3)Es与这些互补群之一中的一个致死等位基因相关，它在二号染色体上的 engrailed（en）位点也发生断裂，并且具有一种显性表型，这可能是由于en在腹部背板前部异常表达所致，而en在正常情况下不在该部位表达。在84D - F区域发现的必需基因在整个区域分布并不均匀；最显著的是，84D1 - 11区域似乎没有必需基因。有人认为该区域缺乏必需基因是由于该区域（1）包含具有非必需功能的基因，以及（2）发生了重复，可能在基因组内部和其他地方都有重复。
