Measuring Male Mutation Bias in Drosophila

Male mutation bias is founded on the idea that most mutations are due to errors during replication. Male gametes, which undergo more cell divisions than female gametes, should similarly accumulate and pass on more mutations than female gametes. This "male mutation bias" has been observed across mammals and in birds. This project focuses on identifying whether male mutation bias also exists in insects and if it does, whether it varies in magnitude between species. We analyzed the genomes from 12 Drosophila species and three outgroup species across eight genomic subsets. Because some species have larger X-chromosomes, due to chromosomal fusions, we conducted analysis both including these species and fused regions, and excluding them. We also analyzed several regions of the genome, some known to be directly affected by natural selection and others expected to experience lower levels of selection, more representative of the neutral mutation rate. For each dataset we computed X/A substitution rate ratios and estimated male mutation bias (alpha). Preliminary results show that some Drosophila species exhibit patterns of substitution on the X and autosomes consistent with male mutation bias while others do not.