An analysis of transvection at the yellow locus of Drosophila melanogaster

Studies of a wide variety of organisms have shown that homologous sequences can exert a significant impact on each other, resulting in changes in gene sequence, gene expression, chromatin structure, and global chromosome arch itecture. Our work has focused on transvection, a process that can cause ge nes to be sensitive to the proximity of a homologue. Transvection is seen a t the yellow gene of Drosophila, where it mediates numerous cases of intrag enic complementation. In this article, we describe two approaches that have characterized the process of transvection at yellow. The first entailed a screen for mutations that support intragenic complementation at yellow. The second involved the analysis of 53 yellow alleles, obtained from a variety of sources, with respect to complementation, molecular structure, and tran scriptional competence. Our data suggest two ways in which transvection may be regulated at yellow: (1) a transcriptional mechanism, whereby the abili ty of an allele to support transvection is influenced by its transcriptiona l competency, and (2) a structural mechanism, whereby the pairing of struct urally dissimilar homologues results in conformational changes that affect gene expression.