AN ANALYSIS OF HUMAN SPERM CHROMOSOME BREAKPOINTS

Sperm chromosome analysis of 19 sperm donors with either normal or bal anced karyotypes was carried out in order to explore the nature of spe rm chromosome structural aberrations. A total of 2,389 cells (range 36 -298/donor) were karyotyped after in vitro penetration of hamster eggs . The median percentage of sperm structural aberrations was 9.3% (SD /- 4.7; range 0% +/- 17.8%), with a total of 247 breakpoints, of which 220 could be characterized fully. Two sets of donors were studied in two different centers: center 1 (United States) and center 2 (Spain). The frequencies of nonrejoined and rejoined chromosome-type aberration s were very similar between center 1 and center 2: 83.6% and 10.0%, an d 75.0% and 10.3%, respectively. Chromatid-type aberrations were more frequent in center 2 (14.7%) than in center 1 (6.4%) (P = .037). Chrom osome 4 had less than the expected number of breakpoints (P < .001). A positive significant correlation was found between sperm breakpoints reported in this study and sites of balanced chromosome de novo rearra ngements detected at prenatal diagnosis and reported in the literature (P = .0001).