The Effects of egg1473 Mutation on \u3cem\u3eDrosophila melanogaster\u3c/em\u3e Fourth Chromosome Recombination Rates

Crossover events are beneficial for organisms because they create genetic variation that can be passed along to future generations. Additionally, proper crossing over is crucial for correct chromosome disjunction. Improper crossing over leads to nondisjunction and aneuploidy – the leading genetic cause of miscarriage and developmental disability in humans. Despite its clear importance, the molecular mechanisms behind meiotic crossover regulation are unknown. Since levels of heterochromatin, areas of densely packed DNA, are thought to be partly responsible for determining meiotic crossover distribution, we hypothesized that reducing heterochromatin levels on the heterochromatin-rich fourth chromosome of Drosophila melanogaster would affect crossover rates on that chromosome. To test this hypothesis, a mutation for the eggless gene, a gene encoding a protein necessary for heterochromatin creation, was used to decrease heterochromatin levels. Phenotypic markers on the fourth chromosome were used to visualize crossovers in the eggless mutant and wild-type backgrounds. To confirm crossover events, polymerase chain reaction-based molecular methods were successfully developed. The experimental eggless crosses are currently underway. When completed, these results will be compared to wild-type data to determine if genetic reduction of heterochromatin levels alters meiotic recombination rate on Drosophila chromosome four