Figure 4.—

Influence of the musculus^PWK X chromosome on abnormal sperm head morphology in experiment 1. (A) Examples of three types of sperm head morphologies observed in N_6–8 males from experiment 1. (B) Sperm head morphologies observed for males with progressively large introgressions of musculus^PWK X chromosome (solid chromosomes). The first genotypic class represents control backcross males with a domesticus^LEWES X chromosome (all open). Sample sizes are given on the left margin and the locations of screened markers are indicated with arrowheads along the bottom. Shading for each genotype indicates uncertainty in recombination breakpoints between surveyed markers. Sperm head morphology is partitioned into four phenotypic classes proceeding from normal to abnormal: (1) normal, (2) flattened head, shortened hook, (3) round head, short or absent hook, and (4) severely abnormal. Severely abnormal head morphologies were grouped together and took on a variety of dramatically altered shapes.