Yes, the environment can affect genes. For example, some genes are sensitive to temperature—like the enzyme that controls the synthesis of black pigment melanin in Siamese cats, which is only active at cool temperatures. The cooler the body part, the darker the pigment; since the body is warmer than the extremities, it remains lighter in color. During the winter if your Siamese cat goes outdoors, the fur may become darker, while Siamese kittens are usually white due to the warmth of the mother’s body.