Inheritance of sperm head abnormality types in mice – the role of the Y chromosome

Abstract

SUMMARY: Four inbred strains of mice were used, differing in the total percentages of spermatozoa with abnormal heads (KE, 22·1%; C57, 26·4%; KP, 7·7%; CBA, 5·5%) and in the frequency distribution of abnormality types, as divided into four arbitrary classes. The most variable class 2 (narrow heads with canals inside the nuclear material) accounted for 47% of all abnormalities in KE strain, was common in CBA (29%) and almost missing in KP and C57 strains. F₁ hybrids from the diallel crosses of these strains exhibited highly significant heterosis effects and significant reciprocal differences in the total percentage of abnormalities. The relative frequency of class 2 ranked in F₁ hybrids in a similar order as calculated from the mid-parental values. After seven generations of backcrosses performed to introduce the Y chromosome from CBA to the genetical background of the KE strain, the total percentage of abnormalities was significantly reduced, although the relative proportion of class 2 was similar to that in KE strain. Also the Y chromosome from C57 strain, introduced into the genetical background of KE strain, caused a significant reduction of total abnormalities, but again the relative frequency of class 2 was not affected. It is concluded that the Y chromosome plays an important role in determining the total percentage of sperm head abnormalities, but does not seem to be involved in influencing specific abnormality types.