Figure 1

Predicted ratios. Predicted ratios of full-length proviruses on the allosome (X or Z) to the autosome under recombination linked and non recombination linked deletion scenarios. Predictions are shown for both the XY sex-determination system and the ZW sex-determination system. For any given bias (β) and sex-determination system we make two predictions as to the allosome-to-autosome ratio of full-length proviruses (p). A value of β greater than one is a male bias and a value of β less than one is a female bias. Under the ZW system (e.g. in birds) both male bias and a lack of recombination may contribute to an excess of ERVs on the Z chromosome when compared to the autosome.