Negative segregation distortion in the SD system of Drosophila melanogaster: a challenge to the concept of differential sensitivity of Rsp alleles.
Negative segregation distortion in the SD system of Drosophila melanogaster: a challenge to the concept of differential sensitivity of Rsp alleles.
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果蝇 SD 系统中的负分离扭曲：对 Rsp 等位基因差异敏感性概念的挑战。
DOI：
10.1093/genetics/125.3.515
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发表时间：
1990
期刊：
影响因子：
3.3
通讯作者：
Hiraizumi,Y
中科院分区：
文献类型：
--
作者：
Hiraizumi,Y
目前基于先前实验结果的分离畸变模型预测，在Sd杂合子Rsp（i）/Rsp（s）男性中，相对于携带不敏感Rsp（i）等位基因的染色体，携带敏感Rsp（s）等位基因的染色体以小于预期孟德尔0.5的频率畸变或传递。本研究提供了一个不发生这种情况的情况，即当雄性的基因型为supp-X（SD）/Y; Sd E（SD）Rsp（i）M（SD）（+）/Sd（+）E（SD）（+）Rsp（s）M（SD）（+）时，其中supp-X（SD）是携带SD活性的一个或多个强抑制子的X染色体，SD（+）E（SD）（+）Rsp（s）M（SD）（+）是标准cn bw染色体。在"授精雌性转移“程序之后，携带标准-X而不是supp-X（SD）染色体的上述基因型的年轻雄性显示SD染色体的k值（在后代中回收的SD染色体的频率）约为0.75，但是对于supp-X（SD）染色体，k值降低到0.36-0.41。排除了几种可能性以外的偏析变形的机制，以解释减少k值。"负分离畸变“的发生被清楚地证明，携带Rsp（i）等位基因的染色体被畸变，但携带Rsp（s）等位基因的染色体没有。这一结果需要对现有模型进行重大修改，甚至需要一个新的分离扭曲机制模型，以适应Rsp等位基因的敏感性或不敏感性。本研究还表明，Sd Rsp（ss）M（SD）（+）/Sd（+）Rsp（ss）M（SD）基因型的雄性几乎完全不育，但当SD活性被supp-X（SD）染色体抑制时，它们的育性显著增加。该结果表明，Sd产物的量不受可用的相互作用位点的限制，也就是说，该量大到足以与两个Rsp（ss）等位基因相互作用。
Current models of segregation distortion based on previous experimental results predict that, in the Sd heterozygous Rsp(i)/Rsp(s) male, the chromosome carrying the sensitive Rsp(s) allele is distorted or transmitted in a frequency smaller than that of the expected Mendelian 0.5 relative to the chromosome carrying the insensitive Rsp(i) allele. The present study presents a case where this does not occur, that is, when the genotype of the males is supp-X(SD)/Y; Sd E(SD)Rsp(i) M(SD)(+)/Sd(+) E(SD)(+) Rsp(s) M(SD)(+) where supp-X(SD) is an X chromosome carrying a strong suppressor or suppressors of SD activity and SD(+) E(SD)(+) Rsp(s) M(SD)(+) is the standard cn bw chromosome. Following the ``inseminated female transfer'' procedure, young males of the above genotype carrying the standard-X instead of the supp-X(SD) chromosome show k values for the SD chromosome (frequencies of the SD chromosome recovered among progeny) of about 0.75, but with the supp-X(SD) chromosome, the k values are reduced to 0.36-0.41. Several possibilities other than the mechanism of segregation distortion to explain the reduced k values are ruled out. The occurrence of ``negative segregation distortion'' is clearly demonstrated, where the chromosome carrying the Rsp(i) allele is distorted, but the chromosome with the Rsp(s) allele is not. This result requires a major modification of the current models or even a new model for the mechanism of segregation distortion to accommodate Rsp allele sensitivity or insensitivity. The present study also shows that males of the genotype, Sd Rsp(ss) M(SD)(+)/Sd(+) Rsp(ss) M(SD), are almost completely sterile, but their fertility is considerably increased when SD activity is suppressed by the presence of the supp-X(SD) chromosome. This result suggests that the amount of the Sd product is not limited with respect to the interacting sites available, that is, the amount is large enough to interact with both of the Rsp(ss) alleles.