Studies on frequency of Y chromatin in human sperm

The preparation and evaluation of human ejaculate smears on cover glasses enables double-sided examination of the individual sperm heads in the fluorescence microscope. By this method of observation the frequency of Y chromatin in the ejaculates of 19 probands increased significantly to between 1.7 and 6.3%. However, the frequency of 50% Y chromatin-positive sperms theoretically to be expected is not found by applying this technique. Furthermore, sexual abstention of at least 14 days leads to a statistically significant decrease of the frequency of Y chromatin. These observations could explain why the data on Y chromatin frequency reported in the literature appear so inconsistent.