Meiotic products of two reciprocal translocations studied by multicolor fluorescence in situ hybridization

The sperm products of two male carriers of reciprocal translocations were studied by fluorescence in situ hybridization (FISH) using a combination of three probes for each translocation. One patient carried a t(2; 18)(p21; q11.2), the other a t(8; 9)(q24.2; q32). The probes selected included a centromeric marker for each chromosome involved in the translocation plus a third probe distal to the translocation breakpoint of one of the translocation chromosomes. This assay identifies alternate, adjacent 1, adjacent 2, and 3:1 types of meiotic products. It allows the identification of recombination events and also estimation of the frequency of diploidy. For the t(2; 18), the frequency of normal and balanced sperm and of adjacent 1, adjacent 2, and 3:1 products was 43.6%, 29.8%, 10.5%, and 12.8%, respectively. Similar segregation patterns had been reported for this donor by direct sperm karyotyping of sperm cells. For the t(8; 9), the frequency of normal and balanced sperm and of adjacent 1, adjacent 2, and 3:1 products was 44.4%, 41%, 3.1%, and 9.4%, respectively. The frequency of complementary adjacent 1 products was statistically different in both the t(2; 18) (P