Detecting signatures of natural selection in genetic data

I report on three studies where I identify signatures of natural selection in humans, and dissect the genetic architecture of complex phenotypic traits in yeast. In chapter 2, I discuss the results of a quantitative trait mapping study, where we showed that yeast growth can be characterized by multiple biologically-relevant growth parameters obtained by fitting yeast growth OD data to a sigmoid function. We identified quantita- tive trait loci (QTL) and gene-gene interactions driving variation in these yeast growth parameters. We analyzed the environment dependence of these QTLs and gene-gene interactions, and identified a common gene, FLO8, which interacts with other genes in an environment specific fashion to affect distinct growth phenotypes. In chapter 3, I describe our published study where we applied quantitative trait locus mapping to wildtype yeast strains, and identified linked clusters of genetic variants that contributed to variation in the sporulation efficiency of these strains. In chapter 4, I describe our work on identifying signatures of natural selection in the human lineage, specifically in the Maasai people in East Africa. Our work suggests that the Maasai have under- gone recent diet induced positive natural selection that may confer protection against hyperlipidemia and cardiac diseases.Ph. D.Includes bibliographical referencesby Aatish Bhati