SEGREGATION ANALYSIS IN A MAN HETEROZYGOUS FOR A PERICENTRIC-INVERSION OF CHROMOSOME-7 (P13-Q36) BY SPERM CHROMOSOME-STUDIES

We have analyzed 140 sperm chromosome complements from a subfertile ma n heterozygous for an inv(7)(p13;q36). Seventy-five percent of the chr omosome complements were not recombinant: 37.9% contained the normal c hromosome 7, and 37.1% contained the inverted chromosome 7. Twenty-fiv e percent of the 140 were recombinant: 7.1% carried a recombinant chro mosome 7 with a duplication p and deletion q, 17.1% carried a recombin ant chromosome 7 with a duplication q and deletion p, and 0.7% carried both recombinant chromosomes. The frequency of structural chromosomal aberrations unrelated to the inversion was 11.4%, and the frequency o f aneuploidy was 2.9%. Both frequencies were not significantly differe nt from those in control donors. Two sperm complements with a second i ndependent, contiguous inversion involving one of the original breakpo ints (q36) were observed (1.4%). The risk of producing chromosomally a bnormal offspring or spontaneous abortions would be 34.3%. The proport ion of X-bearing and Y-bearing sperm was 46.8% and 53.2%, respectively , not significantly different from the expected 1:1 ratio.