Influence of Gene Size and Exon-Intron Structure on Patterns and Rates of Evolution in Drosophila

University Of Iowa, Iowa City IA

Investigators

Abstract

The genetic information of most genes that code for proteins in eukaryotes is not contiguous but split into segments called 'exons' and 'introns'. Exons correspond to sequences with information for the amino acids of the encoded protein while introns are intervening sequences between exons that do not carry information for protein sequence. The number of introns in a gene varies considerably not only among different genes but also when comparing homologous genes between species. Nevertheless, little is known about the causes for intron presence and the evolution of exon-intron structures. Theoretical models of natural selection forecast that, all else being equal, genes with introns might exhibit a selective advantage compared to genes without introns, which would explain the prevalence of introns in most genomes. In this project the PI will investigate this possibility by applying population genetics techniques, both experimental and theoretical. To this purpose, the PI will obtain information of nucleotide variability within species (i.e., polymorphism) and between species (i.e., divergence) in several species of Drosophila and will estimate the efficacy of natural selection's taking advantage of advantageous mutations and eliminating deleterious mutations in four groups of genes classified according to the size of the coding sequence and intron presence/absence. The results from the proposed work will be significant for the field of population genetics and it will give new insight into the forces involved in the evolution of introns and gene structures, and genome size and organization in eukaryotes.