Tandem duplications inDrosophila melanogaster: III. Intrachromosomal exchange of a heterozygous tandem duplication

Abstract

SUMMARYDuring meiosis the two parts of a tandem duplication are able to pair in a double loop instead of pairing with the corresponding region of the homologous chromosome. The frequency of intrachromosomal exchange within this double loop was measured in heterozygous females of tandem duplicationDp(1; 1)Grby the phenotypes of the exceptional F1males. The intrachromosomal exchange frequency is increased significantly by both the ‘interchromosomal effect’ of heterozygous inversions in the autosomes and by a double inversion in the homologousXchromosome. Distribution of the exchange events depends on the pairing situation and its frequency within the double loop. The analysis of clusters of intrachromosomal recombinants observed favours the assumption that this exchange type is exclusively a meiotic event.