This project will improve our understanding of the genetic basis of growth and body size, using whole-genome sequence data and fine-mapping of body mass, in a layer chicken population that we are studying. Growth and body size traits are the paradigmatic examples of complex traits, and important both to animal breeding and adaptation in the wild. We have previously detected strong association with body mass and bone length on chromosomes 4, 6 and 27 in the chicken genome. Fine-mapping them will reveal genes and candidate variants underlying these associations. This project has three aims: 1. To generate whole-genome sequence data on the chicken population to enable fine-mapping. 2. To discover which genetic variants are the best candidates for causing associations with body mass and bone length. 3. To prioritise candidate variants based on their molecular function. This project will fine-map body mass and bone length in chickens using whole-genome sequence and functional genomic data, in order to improve our understanding of the genetic basis of growth and body size.