Partial complementation by murinethaplotypes: deficit of males amongt6/tw5double heterozygotes and correlation with transmission-ratio distortion

Abstract

SummaryTo evaluate whether sex reversal contributes to sex-ratio imbalance amongt6/tw5double heterozygotes, the cross performed by K. B. Bechtol (Genetical Research39, 1982, 79–84),T/t6×T/tw5, was repeated. Significantly more normal-tailed (t6/tw5) females than males were recovered. By contrast, sex ratios were normal among tailless progeny resulting from this cross and among all classes produced by control crosses. Hybridization of a Y-specific DNA probe with genomic DNA from phenotypic females revealed no XY, sex-reversed males. On the genetic backgrounds that generated only moderate transmission distortion oftw5(81–85%), the overall viability of the doubly heterozygous progeny was only 50% and the sex-ratio skew among this class was strong. However, on a genetic background that displayed extremetw5transmission (99%), embryonic viability was more than 80% and the sex-ratio imbalance was weak.