An investigation of some of the factors influencing the results of Y-chromosome detection in blood stains.

The possible significance of some factors with regard to their effect on Y-chromosome detection in blood stains was investigated. (1) It was found that when using centrifugal force instead of a pipette for the extraction of stains on cotton cloth a much higher number of leukocytes was achieved during the first seven weeks of storage. (2) The accidental variation was examined in 10 blood smears from each of 25 males. The standard deviation was found to be independent of the Y-body count (expressing the size of the fluorescing part of the Y-chromosome). Thus, not unexpectedly, the risk of a false negative result (less than or equal to 10%) was highest in those with small Y-chromosomes. This risk was usually infinitesimal. (3) The count in polymorphonuclear leukocytes was found to be lower than in mononuclear leukocytes. The reason for this difference is believed to be due to the irregular shape of the polymorphonuclear leukocytes with overlapping, irregular margins and nuclear projections. (4) The Y-body count in blood smears fixed in 100% methanol was found to decline significantly after a few days of storage. In a comparison with Carnoy's solution the latter was found to be more suitable for fixation.