Genetic Diversity and Demographic Evolution Using <I>SRY </I>Gene Polymorphism in Four Lineages of Ladoum Sheep in Senegal

Abstract

Knowledge of spatial and temporal distribution of genetic diversity within and between populations is a crucial step for establishing strategies management of Animal genetic resources. This study aims to contribute to a better understanding of the genetic structure of local sheep breeds. Specifically, it will characterize the genetic diversity, differentiation and evolution of the <I>SRY </I>gene in four main lineages of Ladoum sheep in Senegal. After alignments and corrections, a total of 42 sequences were used for analysis of <I>SRY</I> genetic diversity and demographic evolution. The standard indices of genetic diversity, genetic differenciation, analyses of hierarchical molecular variance (AMOVA) and demographic tests were compute. Analysis of genetic variability parameters in the overall population revealed a low level of polymorphism in the <I>SRY </I>gene. Haplotypic diversity is much higher than the average nucleotide divergence between all pairs of haplotypes. The genetic distances, as well as the values of the genetic differentiation factor beetween lineages, reveal two genetic groups; one made up of the individuals of “Birahim” and the other, grouping the three lineages individuals. Differences in frequencies of essential proteins for a multitude of functions in the body are observed between the "Birahim" lineage and the others. The comparative trends in genetic diversity indices, the shape of the mismatch distribution curves, demographic indices and demogenetic tests show a rapid and recent expansion population from an ancestral small size. The Z-test analysis of selection revealed that <I>SRY </I>gene is under selection. Unlike “Batling” who is under negative selection, "Birahim" and "Gorgui" are under positive selection. This study has made a significant contribution to understanding the genetic structure of the Ladoum raised in Senegal.