Consider an mRNA strand that has a sequence of base pairs of GUU CUA ACU. Suppose a substitution mutation occurred in the DNA, resulting in the last base in the first codon of the mRNA to be replaced by Cytosine. Using the codon chart below, a) identify which amino acid will now be formed, b) identify whether or not there will be a phenotypic change, and a brief explanation. Your answer should be in 2-4 sentences.

Question

Grading Considerations:

Your answer must include:

Correct amino acid (abbreviation from chart) formed from new mRNA sequence
Explanation on whether or not this would cause a phenotypic change
Your answer should be 2 sentences in length.

Answer 1

The original mRNA sequence GUU codes for the amino acid Valine (Val), but with the substitution mutation, the first codon changes to GUC, which still codes for Valine (Val). Therefore, there will be no phenotypic change since the amino acid sequence remains the same despite the mutation.