DIRECT EVIDENCE FOR SUPPRESSION OF RECOMBINATION WITHIN 2 PERICENTRICINVERSIONS IN HUMANS - A NEW SPERM-FISH TECHNIQUE

Crossover within a pericentric inversion produces reciprocal recombina nt chromosomes that are duplicated/deficient for all chromatin distal to the breakpoints. In view of this fact, a new technique is presented for estimating the frequency of recombination within pericentric inve rsions. YAC probes were selected from within the q- and p-arm flanking regions of two human inversions, and two-color FISH analysis was perf ormed on sperm from heterozygous inversion carriers. A total of 6,006 sperm were analyzed for chromosome 1 inversion (p31q12), and 3,168 wer e analyzed for chromosome 8 inversion (p23q22). Both inversions displa yed suppression of crossing-over, although the amount of suppression d iffered between the two inversions. The recombination frequency of 13. 1% recorded for chromosome 8 inversion was similar to the frequency of 11.4% previously estimated by the human/hamster-fusion method. For ch romosome 1 inversion, the recombination frequency of 0.4% reported her e was below the limits of detection of the fusion technique. The simpl icity of the FISH technique and the ease of scoring facilitate analysi s of a sample-population size much larger than previously had been pos sible.