1. Natural Selection on the Olfactory Receptor Gene Family in Humans and Chimpanzee Chloe Lee

2. Question Human have more than 1000 OR genes, and about 40% have intact (non-mutated) coding region : functional Human have more than 1000 OR genes, and about 40% have intact (non-mutated) coding region : functional 68 to 72% for apes 68 to 72% for apes Comparing the variations at the OR genes with at intergenic region (a stretch of DNA sequences located between clusters of genes that contain few or no genes) Comparing the variations at the OR genes with at intergenic region (a stretch of DNA sequences located between clusters of genes that contain few or no genes)clusters genesclusters genes

3. Method OR genes were obtain from HORDE database OR genes were obtain from HORDE database PCR and DNA sequencing PCR and DNA sequencing LOTS OF STATISTICAL data analysis LOTS OF STATISTICAL data analysis Diversity level by Watterson’s θw, Diversity level by Watterson’s θw, Average number of pairwise differences in the sample Average number of pairwise differences in the sample Ka/Ks: ratio of non-synonymous to synonymous Ka/Ks: ratio of non-synonymous to synonymous Etc Etc

4. Marginal posterior distribution of the directional selection parameter on amino acid replacement mutations the posterior distributions of γ : 0. the posterior distributions of γ : 0. Also 95% std dev of pseudogene is very similar for both species Also 95% std dev of pseudogene is very similar for both species This data indicates that amino acid replacement mutations in pseudogenes have little effect on fitness This data indicates that amino acid replacement mutations in pseudogenes have little effect on fitness A: Chimpanzee B: Human Dotted: pseudognes straight: functional

5. Findings Diversity pattern due to natural selection, not demography. Diversity pattern due to natural selection, not demography. Purifying selection acting on intact OR genes of chimpanzee Purifying selection acting on intact OR genes of chimpanzee Positive selection acting on some of intact OR genes of human Positive selection acting on some of intact OR genes of human Most human genes are under no or little evolutionary constraint, but may evolve under the positive selection. Most human genes are under no or little evolutionary constraint, but may evolve under the positive selection.