Question

Consider an mRNA strand that has a sequenceuuu of base pairs of GUU CUA ACU. Suppose a substitution mutation occurred uuuin the DNA, resulting in the last base in the first codon uuuof the mRNA to be replaced by wCytosine. Using the codon chart below, a) identify which amino acid will now be formed, b) identify whether or not there will be a 9phenotypic change, and a brief explanation. Your answer should be in 2-4 sentences.



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 2-4 sentences in length. In an effort to combat plagiarism, answers longer than 5 sentences will not be considered. Answering concisely and to the point is evidence of your understanding of the topic.
(2 points)

Answer 1

The mutated codon GUC codes for Val (valine). This is a synonymous (silent) mutation—GUU → GUC still specifies valine—so the amino acid sequence and typically the phenotype remain unchanged.