Preferential pairing of sex chromosomes in homotype and heterotype tetraploid silkworm females of sex-limited normal pattern strain, homare

Two types of autotetraploid females of the sex-limited HOMARE strain, homotype (HOMARE × HOMARE) and heterotype(HOMARE ° Tw1), were induced by applying a cold shock to the eggs. The sex chromosome formula of triploid offspring from 2 kinds of tetraploid females could be discriminated by crossing with sch/sch males, which carry the sex-linked chocolate gene. In the triploid progenies of both types, ZWW females a rose in a quite low percentage(0.7%), while the frequency of ZZZ males in the homotype descendant(12.46%) were much higher than that in the heterotype(5.07%). The low occurrence of ZZZ and ZWW triploids revealed that the sex chromosome pairing between Z and Z as well as W and W was more preferential, and the pairing of homologous sex chromosomes in the heterotype tetraploid oocytes was calculated to be 2.8 times as frequent as that in the homotype ones. © 1995, The Japanese Society of Sericultural Science. All rights reserved.