DISTORTION OF MENDELIAN RECOVERY RATIO FOR A MOUSE HSR IS CAUSED BY MATERNAL AND ZYGOTIC EFFECTS

An HSR in chromosome 1 which is found in many feral populations of Mus musculus domesticus was shown in previous studies to consist of a hig h-copy long-range repeat cluster. One such cluster, MUT, showed distor ted transmission ratios when introduced by female parents. MUT/+ offsp ring were preferentially recovered at the expense of +/+ embryos in th e progeny of female MUT/+ x male +/+ but were found at the expected 1: 1 ratio in reciprocal crosses. Preferential recovery of maternal MUT w as due to lethality of postimplantation +/+ embryos. There was no dist ortion of the recovery ratio in MUT/+ x MUT/MUT progeny: maternal MUT and + clusters were present among live implants at a 1:1 ratio. Matern al and zygotic effects therefore contribute to the phenomenon. The mec hanism of their interaction is unknown.