Analysis of human sperm chromosome complements from a male heterozygous for a reciprocal translocation t(11;22)(q23;q11).

A reciprocal translocation between chromosomes 11 and 22 (t(11;22)(q23;q11] is a site-specific translocation that is of particular interest because of the propensity for 3:1 segregation of the chromosomes during meiosis. There have been no published reports of chromosomally unbalanced offspring born as a result of adjacent 1 or 2 meiotic segregations in a heterozygote for this translocation. This could be explained by a meiotic mechanism which produces only 3:1 chromosomal segregations or by differential embryonic survival in which 2:2 adjacent segregations do not produce a viable pregnancy. To distinguish between these two possibilities, sperm chromosome complements from a man heterozygous for this 11;22 translocation were studied. The human sperm chromosomes were analysed after fertilization of zona pellucida-free golden hamster eggs. All possible 2:2 (alternate, adjacent 1, adjacent 2) and 3:1 segregations were observed and these segregations occurred in approximately equal frequencies. The frequency of other chromosome abnormalities, unrelated to the translocation, did not appear to be increased. These results indicate that the 11;22 translocation does not specifically cause 3:1 disjunction of chromosomes but that this segregation of chromosomes is more likely to result in a viable pregnancy.