Sperm segregants from the murine Rb(11.14) heterozygote fertilizing in vivo and in vitro

Segregants of the Rb(11.14) translocation in 17 heterozygous male mice were analyzed in G- and C-banded first-cleavage metaphases after in vivo (n = 440) and in vitro (n = 267) fertilization. Mating intervals of 3 and 14 d provided unaged and physiologically aged sperm for the oocytes, which were from chromosomally normal females. Significantly more normal than balanced sperm segregants were seen in both the in vivo fertilized (P < 0.01) and in vitro fertilized (P < 0.001) study groups. The distortion was elevated in vitro (P < 0.02), unaccompanied by a sex-ratio distortion, and had a segregant distribution that was independent of sperm age; thus it differs from that seen for other translocations. The findings argue for chromosome-specific effects of Robertsonian translocations on sperm function. A significantly (P < 0.05) increased hyperhaploidy rate (unrelated to the translocation) supports the sperm-aging hypothesis.