Biology: Concepts and Investigations 2nd Edition by Mariëlle Hoefnagels

Exercise 22

The shape of a finch's beak reflects the expression of a gene that encodes a protein called calmodulin. A cactus finch has a long, pointy beak; its cells express the gene more than a ground finch, which has a short, deep beak. When researchers boosted gene expression in a ground finch embryo, the bird's upper beak was longer than normal. Develop a hypothesis that explains this finding.