ON THE COMPONENTS OF SEGREGATION DISTORTION IN DROSOPHILA MELANOGASTER

[摘要] The segregation distorter ( SD ) complex is a naturally occurring meiotic drive system with the property that males heterozygous for an SD -bearing chromosome 2 and an SD +-bearing homolog transmit the SD -bearing chromosome almost exclusively. This distorted segregation is the consequence of an induced dysfunction of those sperm that receive the SD + homolog. From previous studies, two loci have been implicated in this phenomenon: the Sd locus which is required to produce distortion, and the Responder ( Rsp ) locus that is the site at which Sd acts. There are two allelic alternatives of Rsp —sensitive ( Rspsens ) and insensitive ( Rspins ); a chromosome carrying Rspins is not distorted by SD . In the present study, the function and location of each of these elements was examined by a genetic and cytological characterization of X-ray-induced mutations at each locus. The results indicate the following: (1) the Rsp locus is located in the proximal heterochromatin of 2R ; (2) a deletion for the Rsp locus renders a chromosome insensitive to distortion; (3) the Sd locus is located to the left of pr ( 2 -54.5), in the region from 37D2-D7 to 38A6-B2 of the salivary chromosome map; (4) an SD chromosome deleted for Sd loses its ability to distort; (5) there is another important component of the SD system, E(SD) , in or near the proximal heterochromatin of 2L , that behaves as a strong enhancer of distortion. The results of these studies allow a reinterpretation of results from earlier analyses of the SD system and serve to limit the possible mechanisms to account for segregation distortion.

[学科分类] 医学（综合）