Mutations in HP1 interact with loss of function Sxl alleles to reduce female viability.

Female viability is markedly reduced in progeny from Su(var)205 mothers and Sxl fathers (Maternal) but not in progeny from Su(var)205 mothers and Sxl− fathers (Paternal). (p**, *). For the third cross, numbers of FM7 classes not presented as the balancer also affects viability (males in particular) and these progeny were not factored in the female to male comparison.