Cytogenetic analysis of spermatozoa in the father of a child with a de-novo reciprocal translocation t(7;9) (q22;p23)

Analysis of sperm chromosomes was carried out in the father of a child with a de-novo reciprocal translocation t(7;9) (q22;p23) by G-banding and chrom osome painting. Sperm metaphases were obtained using the zona-free hamster oocyte-human sperm fusion technique. A total of 138 complements were sequen tially analysed by G-banding and fluorescence in-situ hybridization (FISH). The frequency of spermatozoa with structural chromosome abnormalities (5.1 %) and the estimated conservative aneuploidy (1.4%) were within the range o btained in our control donors (6.9 and 4%). The sex ratio (45.3% X versus 5 4.7% Y) was not significantly different from the theoretical 1:1. A total o f 309 sperm complements was analysed by FISH, 138 sequentially analysed by G-banding-FISH and another 171 analysed by FISH only. The frequencies of st ructural chromosome abnormalities for chromosomes 7 and 9 (0.6 and 0% respe ctively) were not significantly different from those obtained in our contro l donors (0.6 and 0.8%). No spermatozoa with the t(7;9) (q22;p23) were obse rved, showing no evidence for a germ-cell mosaicism. A statistically signif icant, positive association between sperm breakpoints and fragile sites (P = 0.0225) was observed. However, the coincidence between fragile sites and sperm breaks (80%) was not significantly different from that obtained in ou r control donors (79.2%). These results suggest that in this case the risk of structural chromosome abnormalities in further offspring is not increase d, although an association between fragile sites and sperm chromosome break s in the father does exist.