Final answer:
Venom genes in snakes have been recruited from genes expressed in their reproductive organs, brain, and pancreas.
Step-by-step explanation:
Venom genes in snakes have been recruited from genes expressed in all of the above organs: reproductive organs, brain, and pancreas. Snakes produce venom in specialized glands located in their heads, and the genes responsible for producing venom are believed to have originated from genes expressed in other organs. For example, snake venom proteins have been shown to have structural similarities to proteins expressed in the pancreas and brain of non-venomous vertebrates.
This suggests that these genes were repurposed and modified to produce venom in snakes Specifically, genes expressed in the reproductive organs, brain, and pancreas have all been shown to contribute to the development of venom in snakes. This process of gene recruitment is a prime example of how existing genes can undergo duplication and diversification of function.