Skin color is often one of the first traits people notice in

Skin color is often one of the first traits people notice in each other. Studies in zebra fish uncovered a mutation that altered a transport protein and resulted in light-colored fish. This discovery led to the finding that the same gene in humans has a strong influence on skin pigmentation in many populations. A small portion of the human transport protein amino acid sequence is shown below. The upper sequence is associated with darker skin. and the lower sequence is associated with lighter skin. What DNA base-pair change created the light-skin form of the human protein from the gene that coded for the dark-skin form?

Solution

The Correct answer will be GC to AC in the first position of the codon.

As we can clearly see the change in the pigmentation of two amino acid sequence shows change of alanine in the first sequence to threonine in the second one

The sequence of alanine is either GCU,GCC,GCG or GCA. While Threonine, first base is substituted and the sequence becomes ACU,ACG,ACC or ACA.

Therefore the first option is correct. In the First Sequence GC is changed to AC,leading to change of ALANINE to THREONINE I the sequence, which determines pigmentation.