SD-72 has a temperature-sensitive period during spermiogenesis

Abstract

Segregation distorter (SD) chromosomes in Drosophila melanogaster are naturally occurring 2nd chromosomes which produce greatly altered transmission frequencies when present in heterozygous males. The proximate cause of segregation distortion is abortion of spermatids carrying the non-SD homologue. SD-72, a chromosome previously shown to be unaffected by high temperature treatment of spermatocytes, a stage when several SD genotypes are temperature sensitive, has a temperature-sensitive period during spermiogenesis. SD-72/cn bw males exposed to a 24 h pulse of 29.degree. C, then brooded for 24 h, experience a decrease in segregation distortion of approximately 2/3. The timing of the reduction in distortion indicates that the temperature-sensitive period is postmeiotic.