Siamese cats are homozygous recessive for a mutation in the TYR gene, producing a mutated form of the enzyme tyrosinase that leads to pigmented fur. The mutated form of tyrosinase only produces pigment at the extremities of the body. What type of effect is this phenomenon associated with?
Added by Daniela N.
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Step 1: Recognize that pigment production depends on tyrosinase activity, which in Siamese cats is active only at cooler temperatures. Show more…
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Some mutations result in proteins that function well at one temperature but are nonfunctional at a different (usually higher) temperature. Siamese cats have such a "temperaturesensitive" 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.
Some mutations result in proteins that function well at one temperature but are nonfunctional at a different (usually higher) temperature. Siamese cats have such 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.
Sai S.
Melanin is a pigment that is generated by an enzyme called tyrosinase. A mutation in Siamese cats causes tyrosinase to work best at room temperature (~77°F). Use the coloration pattern of Siamese cats to explain why this mutation is classified as "conditional".
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