Multicolor fluorescence in situ hybridization analysis of the spermatozoa of a male heterozygous for a reciprocal translocation t(11;22)(q23;q11).
A reciprocal translocation between chromosomes 11 and 22 is a site-specific translocation that has been seen in many families with no common ancestry. This translocation is of particular interest because balanced carriers have a 0.7-3.7% risk of having children with the supernumerary der(22), resulting from a 3:1 segregation. We have used a three color fluorescence in situ hybridization (FISH) with specific DNA probes to determine the chromosome segregation pattern of a male carrier of a translocation t(11;22)(q23;q11). The probes selected included a centromeric marker for chromosome 11, a marker closely linked to the centromere of chromosome 22, and a third probe distal to the translocation breakpoint of chromosome 22. The results showed that 3:1 segregation is preferential in this patient, with 40.1% of spermatozoa belonging to this segregation type. Alternate segregation followed with 27.4% of analyzed spermatozoa; 17.6% resulted from adjacent 1 and 12.5% resulted from adjacent 2 segregation. We detected 0.5% of presumably diploid spermatozoa. Complementary adjacent 1 products were observed at statistically different frequencies (P = 0.02). Complementary adjacent 2 products without recombination in the interstitial segments were also seen at different frequencies (P = 0.002). In 3:1 segregation, the products containing one chromosome were observed more frequently than those with three chromosomes (P = 0.0001). The 24,+der(22) gamete was seen more frequently than all of the other gametes combined which had 24 chromosomes resulting from 3:1 segregation. The results of this study demonstrate that in this t(11;22) carrier, 3:1 segregation is preferential but not exclusive.
Department of Human Genetics, MCP-Hahnemann University of the Health Sciences, Pittsburgh, Pennsylvania, USA. estop@pgh.auhs.edu
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D000328:Adult; D002874:Chromosome Mapping; D002880:Chromosomes, Human, Pair 11; D002892:Chromosomes, Human, Pair 22; D006580:Genetic Carrier Screening; D005819:Genetic Markers; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D013094:Spermatozoa / Q000473:pathology*; D014178:Translocation, Genetic
D005819:Genetic Markers