A difference in dry mass between the heads of X- and Y-bearing human spermatozoa.

An integrating microinterferometer was used to measure the dry mass of sperm heads. The dry mass was found to be proportional to DNA content, and thus provides a useful method of estimating sperm DNA content. Using this technique we have confirmed that human spermatozoa which show none and one quinacrine-fluorescent spot are X- and Y-bearing respectively. However, the measurements suggest that many of the spermatozoa with two quinacrine-fluorescent spots are not YY-bearing, as previously thought, but might be incompletely condensed Y-bearing spermatozoa.