In other words, about 9 times as many segments had incompatibility alleles affecting male fertility. Incompatibility alleles affecting male fertility accumulate much faster than those affecting female fertility, supporting the differential accumulation theory. C. Differential Accumulation on X chromosome. Wu et al. performed a similar experiment introgressing X-chromosome segments from D.mauritiana into D. simulans . Results indicate that there are more than 40 incompatibility genes on the X-chromosome contributing to male sterility.
Results support the differential accumulation theory.
As a general phenomenon, Haldane's rule seems to be caused by several different phenomena. In some cases, it seems to be due to the type of recessivity of incompatibility interactions envisioned by Muller's theory. One obvious pattern that emerged was that closely related taxa had relatively similar sequences for a given protein, while more distantly related taxa had more divergent sequences for the same protein. This pattern forms the basis for phylogeny reconstruction using molecular sequences, which is considered in the next lecture. The figure below plots this data for a globin.