Determining functions of gene duplications from Drosophila X chromosomes to autosomes
Vanchinathan, Rahul Arvind
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Gene duplication plays a vital role in evolution. It provides a second copy of a gene which can be selected upon to obtain a novel function or split the function of the original gene. Although genes can duplicate to and from any chromosome, an unusually high number of duplicated genes from the X chromosome to autosomes is seen in Drosophila. The ancestral copies of these duplications have widespread expression, while the derived copies have testis-biased expression. Additionally, it is known that expression of X-linked genes is downregulated in spermatogenesis. We predict that these duplications alleviate downregulation of the original X-linked genes in spermatogenesis, allowing the genes to be expressed optimally during spermatogenesis. One way to test our hypothesis is to determine the function of both duplicated copies. Drosophila pseudoobscura provides a good model for this experiment, because its X chromosome acts as a disproportionate source of duplicated genes. We study duplicated genes in D. pseuodoobscura that also have a single, orthologous copy in Drosophila melanogaster. Thus, we can use GAL4-UAS to knock down the copy in D. melanogaster and attempt to rescue the knockdown with copies from D. pseuodoobscura. We determined that ubiquitous knockdown of a target gene results in death, and testis-specific knockdown results in infertility. We also established that insertion of a rescue gene does not affect fertility or viability, verified by chi-square analysis. With these controls completed, we are creating flies with both knockdown and rescue gene to test if the knockdown can be rescued.