Heterochromatin and multiple inversions in a Drosophila chromosome.

A chromosomal polymorphism is described from a Maui (Hawaii) population of D. disjuncta. The acquisition of an extra heterochromatic segment in a mitotic chromosome is specifically associated with the presence of multiple inversions in the same chromosome. This suggests the possible effect of a chromosomal break-point within the area of centromeric heterochromatin in causing an increase in the amount of repetitive DNA. The possibility exists that the extra heterochromatin may play a role in the suppression of gene recombination in a certain region of the chromosome and/or in strengthening pairing of the inversion-laden chromosome with its normal homologue. This may reduce the changes of sterility due to nondisjunction during meiosis.