Final answer:
Heat-shock proteins are gene functions that can affect a lizard's cold tolerance.
Step-by-step explanation:
The gene function that might affect a lizard's cold tolerance is heat-shock proteins. Heat-shock proteins help protect cells from damage caused by extreme temperatures. When exposed to cold temperatures, lizards can produce more heat-shock proteins to increase their tolerance to the cold.
For example, temperature-sensitive proteins are at work in other animals like arctic foxes and rabbits. These animals have white fur in the winter and darker fur in the summer. The protein product of the gene that determines their fur color does not fold correctly at colder temperatures. This mutation, which caused the change in fur color, was advantageous to these species as it helped them blend in with their environment.
Therefore, heat-shock proteins are gene functions that can affect a lizard's cold tolerance.