MEIOTIC SEGREGATION, RECOMBINATION, AND GAMETE ANEUPLOIDY ASSESSED INA T(1-10)(P22.1-Q22.3) RECIPROCAL TRANSLOCATION CARRIER BY 3-PROBE AND 4-PROBE MULTICOLOR FISH IN SPERM

Meiotic segregation, recombination, and aneuploidy was assessed for sp erm from a t(1;10)(p22.1;q22.3) reciprocal translocation carrier, by u se of two multicolor FISH methods. The first method utilized three DNA probes (a telomeric and a centromeric probe on chromosome 1 plus a ce ntromeric probe on chromosome 10) to analyze segregation patterns, in sperm, of the chromosomes involved in the translocation. The aggregate frequency of sperm products from alternate and adjacent I segregation was 90.5%, and the total frequency of normal and chromosomally balanc ed sperm was 48.1%. The frequencies of sperm products from adjacent II segregation and from 3:1 segregation were 4.3% and 3.9%, respectively . Reciprocal sperm products from adjacent I segregation deviated signi ficantly from the expected 1:1 ratio (P < .0001). Our assay allowed us to evaluate recombination events in the interstitial segments at adja cent II segregation. The frequencies of sperm products resulting from interstitial recombination in chromosome 10 were significantly higher than those resulting from interstitial recombination in chromosome 1 ( P < .006). No evidence of an interchromosomal effect on aneuploidy was found by use of a second FISH method that simultaneously utilized fou r chromosome-specific DNA probes to quantify the frequencies of aneupl oid sperm for chromosomes X, Y, 18, and 21. However, a significant hig her frequency of diploid sperm was detected in the translocation carri er than was detected in chromosomally normal and healthy controls. Thi s study illustrates the advantages of multicolor FISH for assessment o f the reproductive risk associated with translocation carriers and for investigation of the mechanisms of meiotic segregation of chromosomes .