INTERCHROMOSOMAL EFFECTS AND SEGREGATION

Abstract

It has been proved for Drosophila melanogaster that the interactions at meiosis between nonhomologous chromosomes that are structurally heterozygous result in the production of dominant lethals as well as of primary nondisjunction. Such interactions may occur between any 2 (or 3) pairs of structurally heterozygous chromosomes and need not involve the X chromosomes. Not only does nondisjunction of X chromosomes occur but also nondisjunction of autosomes. It is shown that the preponderance of dominant lethals cannot be accounted for by the production of eggs deficient in sex chromosomes or by multiple-strand crossing over within inverted sequences of either X chromosomes or autosomes. A hypothesis that predicted these findings, and which will partially account for an interchromosomal effect on crossing over, is briefly described.