Polymorphism of centromeric heterochromatin and its relationship to chiasma formation in the paracentromeric regions of murine chromosomes.

A hypothesis suggesting an evolutionary significance of centromeric heterochromatin polymorphism, which presumed the suppression of genetic crossing-over in the paracentromeric chromosome regions, was experimentally tested. The data obtained do not support the hypothesis; the frequency of paracentromeric chiasmata in two inbred mouse strains (differing in centromeric heterochromatin pattern) is not higher than in their F-1 hybrids. C-bands staining of centromeric heterochromatin allowed the distinction of two types of paracentromeric chiasmata. One of them--pseudochiasmata--is probably the consequence of centromeric heterochromatin affinity rather than the result of the preceding crossing-over.