No evidence of sex-ratio meiotic drive associated with the X -linked In(1)Be inversion in Drosophila melanogaster

Sex-ratio (SR) X chromosomes are selfish genetic elements that increase the rate of X chromosome transmission in species with a heterogametic sex, violating Mendel's first law of segregation. In particular, heterogametic males carrying SR X chromosomes produce a greater number of X-bearing sperm than Y-bearing sperm and thus produce a greater number of female than male offspring. SR X chromosomes have been observed in several taxa, including multiple Drosophila species. However, no convincing examples of a strong SR X chromosome have been identified in Drosophila melanogaster. There have been few reports of weak SR X chromosomes segregating in D. melanogaster, including speculation of the X-linked inversion In(1)Be being associated with an SR phenotype. We sought to investigate if the In(1)Be inversion is associated with an SR by measuring the offspring SR in genetically controlled experiments. In our experiments, we found no significant differences in SR between karyotype or across our generated lines, suggesting that in the genetic background we used, there is no SR phenotype associated with the In(1)Be inversion.