Question

QTL mapping and GWAS are both methods to scan the entire genome to find loci that contribute to phenotypic variation in complex traits of interests. However, QTL studies typically use a much smaller number of markers than in GWAS. Briefly describe why the GWAS method requires so many more markers.

Answer 1

The GWAS method requires many more markers as compared to the QTL method and this is one of the disadvantages of using this method for scanning the genome. It uses multiple markers as it is more effective in understanding an association between the genomic trait and the trait that might be associated with it as compared to the connection understanding through use of single marker. With use of multiple markers, it helps in better understanding of genetic components that are associated with complex diseases. The method generally uses single nucleotide polymorphism which is actually single base pair changes in the DNA sequence and it helps in identifying frequency in human genome. The reason of using multiple markers also lie in the fact that it helps in evaluating the association that is there between the genotyped marker and the phenotype across wide range of individuals.