January 16, 2020

5:00 pm TLSB 1100

EcoEvoPub

" Graduate Student Presentations "

Jesse Garcia

Department of Ecology and Evolutionary Biology, UCLA, Lohmueller Lab

 “Detecting the impact of deleterious variation and Hill-Robertson Interference on genome evolution”

Though the theoretical foundation for the expected value of linkage disequilibrium (LD) between two neutral loci has been established, expectations of LD for large numbers of physically linked variants affected by negative selection remain elusive. Forces like Hill-Robertson Interference and negative epistasis are expected to lead to deleterious mutations being found on distinct haplotypes, thus creating an excess of negative LD between derived deleterious alleles. However, the extent to which these forces shape genome-wide patterns of LD is poorly understood. In this study, we assess how the strength of purifying selection on multiple linked loci affect LD and other population genetic analyses. First, we use forward-in-time simulations to examine the extent to which selection might impact patterns of LD. We find that the dominance coefficient and selection strength of mutations jointly affect the impact of selection on LD. Specifically, under models where deleterious mutations have multiplicative effects on fitness, deleterious variants less than 10kb apart tend to be carried on different haplotypes, generating an excess of negative LD relative to pairs of synonymous SNPs. Our simulations predict that this is due to the relatively low frequency of recombination between loci at these distances. In contrast, for recessive mutations, there is no consistent ordering of how selection coefficients affect r² decay. Next, we show that in empirical data of modern humans (1000 Genomes Project), LD among derived nonsynonymous SNPs is on average more negative compared to pairs of derived synonymous variants. Lastly, we introduce a new statistic H^R_(j) which allows us to detect interference with unphased genotype datasets. Our findings suggest that interference or negative epistasis play a pervasive role in shaping patterns of LD between deleterious variants in the human genome and ultimately influence population genetic inference.

 Rachel Turba

Department of Ecology and Evolutionary Biology, UCLA, Jacobs Lab

 “Science Communication: the good, the bad and the ugly”

We never had more access to information than today, and yet we are still faced with people who believe the Earth is flat, that evolution is not real, and vaccines are not worth it. Where science communication is falling short? Are we doing it wrong? Is there a right way? Do we want people to believe in scientists, or do we want them to understand how science works, and why it works? During this time, I want to create a space where we can debate more the role of science communication, the relevance of “facts” and people’s worldviews in forming decisions, and one way that I think would be really good to start thinking about science communication, but ultimately, how we do science ourselves.

Thursday, January 16th, 2020 @ 5 PM

1100 Terasaki Life Sciences Building [TLSB]