Question

Some mutations result in proteins that function well at one temperature but are non-functional at a different (usually higher) temperature. Siamese cats have a "temperature-sensitive" mutation in a gene encoding an enzyme that makes dark pigment in the fur. The mutation results in the breed's distinctive point markings and lighter body color (see the photo). Using this information and what you learned in the chapter, explain the pattern of the cat's fur pigmentation.

Short answer

The mutation is the reason for the different fur pigmentation in the Siamese cat. The temperature-sensitive mutation in the enzyme tyrosinase mediates melanin production, and thus there are differences in the body color.

Step-by-step solution

Description of mutation

A mutation is an undesirable change that takes place in the gene codes of a particular protein.The mutation taking place in the coding regions tends to change the genetic characteristics of the particular organism.

Mutation in the non-coding region of the genetic material does not alter the body mechanism to a greater extent.

Description of Siamese cat fur pigmentation

Dark-colored fur is present in the feet, tails, and some parts of the face in Siamese cats due to the melanin pigment. This pigment gives rise to the two-color shade in the cat's body.

The lighter shade present in the body segment of the Siamese cat is due to the lesser secretion of melanin.

Temperature-sensitive mutation resulting in fur pigmentation

Tyrosinase is the enzyme that works effectively at room temperature. The temperature-sensitive mutation alters the tyrosinase enzyme to work in lower or cooler temperatures.

The cat's body parts, such as the tail, feet, and face, having cooler temperatures, may have darker pigmentation due to the overproduction of melanin mediated by the tyrosinase enzyme.

The rest of the body, having a higher temperature, tends to have a lighter color since the mutated tyrosinase does not work properly at a higher temperature to produce melanin.