Question

Imagine a species whose eye color is determined by a receptor molecule called EyeC. When EyeC is not activated, cAMP levels in the cell are low and yellow pigment is produced. When EyeC is activated by the binding of a signal molecule, cAMP levels rise and blue pigment is produced.

The Q allele codes for a version of EyeC that responds to signal molecules and therefore turns on and off, resulting in green eye color (from both blue and yellow pigment). The P allele codes for a version of EyeC that is ALWAYS activated, even when signal molecules are not present.

Assuming EyeC functions similarly to MC1R, which of the following statements is the best prediction of the dominance relationship between alleles P and Q as well as the phenotype for PQ individuals?

  

P is dominant over Q, and the eye color of PQ individuals is blue.

   

P is dominant over Q, and the eye color of PQ individuals is yellow.

   

Q is dominant over P, and the eye color of PQ individuals is blue.

   

P and Q are codominant, and the eye color of PQ individuals is green.

Answer 1

Ans : Option 4

P and Q are codominant, and the eye color of PQ individuals is green.

Reason : EyeC is activated by the binding of a signal molecule. Q allele codes for a version and eye color will be blue when binds to signal molecule. In the absence of signal molecule EyeC is not activated but exhibit P allele and will exhibit eye color as yellow. Therefore both Q and P allele is present in the EyeC and they are turned on or off in response of the binding of EyeC binding to signal molecule. Therefore P and Q are codominant and the eyecolor will be the combination of two alleles(P and Q), and the eye color of PQ individual is green.