History and significance of the chicken genome sequence Literature review

Abstract

Summary Background: The authors review the literature on the history and main achieve ments of chicken genome sequencing, and the possibilities and advantages of the application of chicken as an animal model. The threat of decreasing chicken genetic diversity is also discussed. Material and Methods: The whole genome sequence of chicken was published in 2004, first of all birds and farm animals. The chicken genome is only half the size of mammalian genomes, and it is packed into 78 chromosomes (2n) of dif ferent size, that can be roughly divided to macro and micro chromosomes. Also first of all animal species, Mendelian inheritance was demonstrated in chickens. The construction of a 600 000 single nucleotide polymorphism containing genotyping array was made possible as a result of genome sequencing efforts. Genotyping arrays are potential tools for breeders to improve chicken produc tion. Furthermore, chicken genome mapping remarkably facilitated the genome sequencing of other bird species. As average recombination rate in chicken is higher compared to mammals, chicken is an ideal animal model also for genetic mapping studies. Results and Discussion: Up to date, 6633 quantitative trait loci (QTL) have been described in chicken, of which 4677 are in association with meat and egg pro duction (growth, fatness, meat and egg quality), 1118 with exterior (pigmenta tion, behaviour), 629 with health (disease susceptibility, mortality), and 209 with physiology (blood parameters, excretion) traits. Genetic diversity in the species has been significantly reduced due to inten sive commercial selection for improved meat or egg production. Nearly half of ancestral alleles are lost in modern breeds and hybrids. Diversity loss was more remarkable in egg type compared to meat type chicken. In their research, the authors aim to determine the genotype frequencies and growth-related effects of different Spot14α, IGF1, IGFBP2, DRD1, and SST poly morphisms in indigenous Hungarian chicken breeds and in modern hybrids