Abstract
The eyes absent (eya) gene in the fruit fly Drosophila melanogaster is required for normal eye development. Loss of eya function causes the adult compound eye to become reduced or completely absent. However, specific combinations of various eya alleles demonstrate partial complementation where the eyes can return to nearly full size. This complementation is dependent on chromosome pairing, and therefore is an example of a transvection effect. Rearrangements that unpair two complementing eya alleles disrupt complementation, and trans-heterozygous rearrangements with similar breakpoints that restore pairing also restore complementation. It has been suggested, based on the analysis of a single zeste allele, that transvection at eya requires normal zeste function. Here, we extend this study to analyze the effects of several zeste alleles on transvection at eya. Loss-of-function mutations zae(bx), za, and zv77h have a disrupting effect on eya complementation. The zae(bx) mutation results in a minor decrease in eye-size compared to z+, while the zv77h mutation results in about half-sized eyes and the za mutation results in about quarter-sized to half-sized eyes. The gain-of-function mutation z1 has no effect on eya complementation. This study will be helpful in better understanding the structure and dynamics of chromosomes.