Chromosome complements in 695 sperm from three men heterozygous for reciprocal translocations, and a review of the literature.

Abstract

Sperm chromosome complements were analysed in three men heterozygous for reciprocal translocations. A total of 695 sperm were karyotyped after in vitro penetration of hamster oocytes: 275 sperm from t(7;20)(q33.2;p13), 268 from t(3;11)(q25.3;q25) and 152 from t(15;22)(q26.1;q11.2). All possible 2:2 and 3:1 meiotic segregations were observed for all three translocations. The frequencies of alternate, adjacent 1, adjacent 2, and 3:1 segregations were 38%, 40%, 16%, and 5% for t(7;20); 48%, 46%, 6%, and 1% for t(3;11); and 34%, 40%, 22%, and 4% for t(15;22), respectively. Within the alternate segregation, the number of normal sperm was not significantly different from the number of sperm carrying a balanced form of the translocation for any of the translocations, as theoretically expected. The percentage of sperm with an unbalanced form of the translocation was 62% for t(7;20), 52% for t(3;11) and 66% for t(15;22). Sperm chromosome complements were observed in all three translocations that could be attributed to crossing-over in the interstitial segment, although nondisjunction at anaphase II could also account for the complements. There was no evidence for an interchromosomal effect in any of the translocations since the frequencies of numerical abnormalities unrelated to the translocation were within the normal range of control donors. Data from a total of 27 reciprocal translocations studied by sperm chromosomal analysis were reviewed.