Question

part c
why did kingsley and his team cross marine and freshwater sticklebacks?
to test whether pitx1 was involved in the formation of pelvic spines.
to compare the pitx1 protein - coding sequence from fish with and without pelvises.
to find the location of the gene(s) causing the difference between stickleback populations with and without spines.
to understand when in embryonic development the gene(s) for making a pelvis is/are active.

Explanation:

The question is about the purpose of crossing marine and freshwater sticklebacks. The key is to understand the scientific context of gene - function research. Testing whether a gene (Pix1 here) is involved in a trait (pelvic spine formation) is a common genetic experiment approach. By crossing different populations (with and without a trait), researchers can analyze the role of specific genes.

Answer:

To test whether Pix1 was involved in the formation of pelvic spines.