INTRACHROMOSOMAL EXCHANGE AT THE BAR LOCUS IN DROSOPHILA

Abstract
Genetic and cytological analyses of 29 bar locus exceptions that were nonrecombinant for marker loci reveal that 18 of these changes were associated with discrete loss or gain of 16A members of the salivary chromosome. In addition two such exceptions were identified among progeny of hemizygotes carrying an X-chromosome homologue deficient for 16A chromatin. From this and other evidence it appears that these nonrecombinant exceptions are not the result of multiple exchanges (negative interference). Rather, they support the model for intrachromosomal exchange.