Animal Molecular Breeding 2024, Vol.14, No.1, 10-18 http://animalscipublisher.com/index.php/amb 13 Conducting a GWAS usually involves the following steps: Sample collection: selecting a sufficient number of samples from case and control groups. Genotyping: Genotype all samples using high-throughput sequencing technology to obtain genome-wide genetic marker information. Association analysis: Statistical methods are used to analyze the strength of association between each genetic marker and the disease, and identify genetic variants that are significantly associated with the disease. Validation of results: The results of the association analysis are validated by independent sample sets or further functional studies. 2.2 Genetic markers and mapping of the poultry genome Genetic markers are specific DNA sequences in the genome that can distinguish between the genetic backgrounds of different individuals, and are often used as "landmarks" for identifying and tracing genetic material. In mapping the poultry genome, genetic markers help scientists to localize genes or gene regions associated with disease resistance. Mapping the poultry genome involves mapping genetic markers to known genomic locations and constructing genetic linkage maps and physical maps. This process is critical to the success of GWAS because it ensures that genetic variants are correctly associated with specific genes or gene regions. 2.3 How to identify genetic variants associated with disease resistance GWAS identifies genetic variants associated with disease resistance by comparing differences in genetic markers between case and control groups. These variants may be located within genes that encode important proteins or in non-coding regions that regulate gene expression. Statistical association: by calculating the difference in the distribution of genetic markers between case and control groups, GWAS can identify genetic markers that are significantly associated with disease resistance. Genes near these markers may be directly involved in disease resistance mechanisms (Pirnay et al., 2021). Bioinformatics analysis: through bioinformatics tools and databases, researchers can further analyze the functions of genes near these markers to reveal their roles in disease resistance. Experimental validation: Ultimately, functional genomics experiments (e.g., gene knockout, gene expression analysis, etc.) are used to validate the specific role of these genes or genetic variants in disease resistance. In summary, GWAS provides a powerful tool for identifying genetic variants associated with disease resistance in poultry on a genome-wide scale. The mapping and association analysis of genetic markers not only enables the discovery of new disease resistance genes, but also provides an in-depth understanding of the function of these genes in the organism, providing a scientific basis for poultry disease prevention, control and breeding. With the advancement of gene sequencing technology and the development of bioinformatics methods, the application prospect of GWAS will be broader and its contribution to the poultry industry will continue to grow. 3 Foundations of Genome-Wide Association Studies (GWAS) 3.1 Specific case studies In recent years, genome-wide association studies (GWAS) have become an important tool in poultry disease resistance research, helping scientists to understand poultry resistance to diseases at the genetic level. Avian Influenza is a disease that severely affects the poultry industry and its viruses are highly mutable, making vaccine development and disease control extremely difficult. In an effort to find natural resistance to avian influenza in poultry, a GWAS analysis of chickens was executed with the aim of identifying genetic markers and genes associated with resistance to avian influenza.
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