Sperm chromosome analysis in the father of a child with a de-novo reciprocal translocation t(11;15)(q12;q22) by G-banding and fluorescence in-situ hybridization

Analysis of sperm chromosomes by G-banding and two-colour fluorescence in-situ hybridization (FISH) was carried out in the father of a child with a de-novo reciprocal translocation t(11;15)(q12;q22). Sperm chromosome complements were obtained after in-vitro fusion of zona-free hamster oocytes and donor spermatozoa. A total of 112 sperm complements was first analysed by G-banding. The frequency of structural chromosome aberrations (9.8%) and the conservative frequency of aneuploidy (0.0%) were not significantly different from those obtained in our control donors. The proportions of X-bearing (53.2%) and Y-bearing (46.8%) spermatozoa were not significantly different from the expected 1:1 ratio. A total of 313 sperm complements was analysed by two-colour FISH. The frequency of structural abnormalities for chromosomes 11 and 15 was 3.2 and 0.3% respectively. The frequency of rearrangements for chromosome 11 was statistically significant when compared with control donors (0.4%) (P < 0.0001). No spermatozoa with the t(11;15)(q12;q22) translocation were observed, showing no evidence for a germ-cell mosaicism. These results suggest that the de-novo involvement of chromosome 11 in a structural rearrangement is not random, and that in this patient an increased risk of de-novo structural chromosome abnormalities in further offspring does exist.