[Heterochromatin of the human Y chromosome as an example of selfish DNA]

The nature of human Y-chromosome of Q-positive heterochromatic region is discussed. Both the authors data and those from literature show the existence of human population polymorphism with respect to the appearance of this region which consists of one or several bright fluorescent blocks. Their multiplication results probably from an unequal sister-strand crossing-over. Absence of these blocks has no visible phenotypic effect. Their extra multiplication affects the embryonal and possibly postnatal psychic development. It is supposed that Q-positive heterochromatin is an example of selfish DNA in the human genome.