What is a key difference between the two major stickleback loci associated with armor variation, EDA and Pitx1_Pel?

What is a key difference between the two major stickleback loci associated with armor variation, EDA and Pitx1_Pel?

• A. EDA mainly controls lateral plates, while Pitx1_Pel controls pelvic spine development; both show population-specific divergence.
• B. EDA controls pelvic spines; Pitx1_Pel controls lateral plates.
• C. They affect same trait identically.
• D. Pitx1_Pel controls head size.

Answer: (A)

The key idea is that different genetic regions tune different parts of the armor. EDA mainly controls the development of the lateral plates along the sides of the fish, so variation at this locus changes how many or how large those plates are. Pitx1_Pel, on the other hand, regulates the pelvic region—the pelvic spine and girdle—so variation here changes pelvic armor rather than lateral plates. In sticklebacks, both loci show population-specific divergence because freshwater and marine populations face different ecological pressures, leading changes in these distinct traits rather than a single, shared effect. The correct statement captures that EDA affects lateral plates and Pitx1_Pel affects pelvic spines, with each showing divergent evolution in different populations.

The key idea is that different genetic regions tune different parts of the armor. EDA mainly controls the development of the lateral plates along the sides of the fish, so variation at this locus changes how many or how large those plates are. Pitx1_Pel, on the other hand, regulates the pelvic region—the pelvic spine and girdle—so variation here changes pelvic armor rather than lateral plates. In sticklebacks, both loci show population-specific divergence because freshwater and marine populations face different ecological pressures, leading changes in these distinct traits rather than a single, shared effect. The correct statement captures that EDA affects lateral plates and Pitx1_Pel affects pelvic spines, with each showing divergent evolution in different populations.