MEIOTIC SEGREGATION IN MALES HETEROZYGOTE FOR RECIPROCAL TRANSLOCATIONS - ANALYSIS OF SPERM NUCLEI BY 2-COLOR AND 3-COLOR FLUORESCENCE IN-SITU HYBRIDIZATION

The meiotic segregation of chromosomes was analysed in three reciproca l translocation carriers, using FISH on interphase spermatozoa. The se gregation pattern was first studied in 27,844 spermatozoa from two sib lings carrying the reciprocal translocation t(6;11)(q14;p14). Three ce ntromeric probes, specific for chromosomes 6, 11 and I, were simultane ously hybridized so that all centric fragments as well as the ploidy o f each cell could be determined by three colour FISH. For both subject s, the respective frequencies of alternate/adjacent 1, adjacent 2, 3:1 and 4:0 segregation modes were 88%, 9% , 3% and <1%. In another recip rocal translocation t(2; 14)(p23.1;q31), a two colour FISH analysis wa s performed on 4,610 spermatozoa, using a chromosome 2 centromeric pro be and a YAC probe located on the centric fragment of chromosome 14. F requencies of alternate/adjacent I, adjacent 2, and 3:1 segregations w ere 89%, 5.2%, and 5.8% respectively. The segregation of chromosomes X , Y and 1 were also analyzed with three colour FISH on the spermatozoa from all three translocation carriers, in order to detect an interchr omosomal effect. Aneuploidy rates for the X and Y chromosomes were fou nd to be in the same range in the three translocation carriers. and co ntrol donors, but disomy 1 rates were slightly increased in the transl ocation carriers.