In stickleback research, what is the primary purpose of QTL mapping?

• A. To locate genomic regions associated with variation in adaptive traits
• B. To measure metabolic rates
• C. To determine migration patterns
• D. To assess mating preferences

Answer: (A)

Locating genomic regions that influence variation in adaptive traits is what QTL mapping does in sticklebacks. This approach links differences in observable traits across individuals to specific parts of the genome by crossing fish with different phenotypes, genotyping their offspring at many markers, and testing which markers co-segregate with trait variation. The regions that show a strong association point to where genes affecting the trait reside, revealing the genetic architecture of adaptation. In sticklebacks, this has helped uncover how multiple genomic regions contribute to differences between marine and freshwater populations, such as armor plating and body shape, illustrating how genetic variation underlies adaptive change. Other options describe measurements or patterns not defined by the primary goal of QTL mapping, which is to map trait variation to genomic regions.