NONDISJUNCTION IN HUMAN SPERM - RESULTS OF FLUORESCENCE IN-SITU HYBRIDIZATION STUDIES USING 2 AND 3 PROBES

Fluorescence in situ hybridization using two or three probes was utili zed to estimate the incidence of diploidy, the incidence of disomy for the sex chromosomes and chromosomes 16 and 18, and the proportion of Y- and X-chromosome bearing sperm, in a series of normal males. Our re sults demonstrate the importance of using an approach capable of disti nguishing disomy from diploidy, as most donors had levels of diploidy higher than the disomy levels of individual chromosomes. Our analyses suggest the existence of chromosome-specific mechanisms of paternal no n-disjunction, as sex chromosome disomy was approximately 1.5 times as common as disomy 16, and over two times as common as disomy 18. In st udies of gametic sex ratio, we found little evidence for marked deviat ion from an expected 1:1 ratio.