The influence of mutations on chromosome 17 upon the segregation of homologues in female mice heterozygous for Robertsonian translocations

Abstract

Summary: The influence of mutations in chromosome 17 upon the segregation of the metacentric and acrocentric homologues in the progeny of female mice heterozygous for Robertsonian translocations Rb(8.17)11em and Rb(16.17)7Bnr was studied. Genetic analysis indicated that the portion of non-Rb (normal karyotype) progeny from mothers heterozygous for mutations tf, qk, t¹² was weakly different from the 50% Mendelian expected level (55–57%). Introduction of mutations T, Fu^Ki, Fu, t⁶ into the female genotype caused a stronger segregation distortion and an increase in the portion of progeny with normal karyotype (63–67%). From the data on embryonic mortality and cytogenetic observations it is concluded that a distortion of equal transmission arises before M II of meiosis. Consequently, the preferential distribution of the metacentric chromosome to the polar body during the first meiotic division is relevant to the observed segregation distortion.