FLOW CYTOMETRIC DETECTION OF UNBALANCED RAM SPERMATOZOA FROM HETEROZYGOUS 1 20 TRANSLOCATION CARRIERS

Flow cytometric analysis of enzymatically decondensed, DAPI-stained sp ermatozoa was performed to confirm the suspected production of unbalan ced spermatozoa in heterozygous rams carrying a 1;20 translocation. Hi gh-precision flow cytometry (coefficient of variation, 0.6-0.8 %) with a PAS II flow cytometer depicted Y- and X-chromosome-bearing spermato zoa from three cytogenetically normal rams as two distinct peaks. The difference in DNA fluorescence intensity between the gonosomes average d 4.8%. Analysis of sperm samples from three heterozygous 1;20 translo cation carriers yielded histograms with five peak distributions. The i ndividual peaks were attributed to spermatozoa with a normal, balanced , and unbalanced chromosomal status. Peaks within Y- and X-spermatozoa populations were distributed in a ratio of 1:2:1 and were almost comp letely separated, with a coefficient of variation of 0.5-0.6%. Owing t o the relative size of the translocated chromosomal segment (2.4% of t he total DNA content, as determined from the flow cytometric data), hi stograms with five instead of the expected six peaks were observed.