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) identity which amino acid will now be formed, and b) explain why this mutation would not result in a phenotypic change. Your answer should be in 2-4 sentences • Correct amino acid (abbreviation from chart) formed from new mRNA sequence

Question

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) identity which amino acid will now be formed, and b) explain why this mutation would not result in a phenotypic change. Your answer should be in 2-4 sentences • Correct amino acid (abbreviation from chart) formed from new mRNA sequence

• Explanation on why this mutation would not have any effect on the phenotype of the organism

Answer 1

a) The new mRNA sequence after the mutation is GUU CUA ACC. According to the codon chart, this codon still codes for the amino acid Leucine (Leu).

b) This mutation would not result in a phenotypic change because the amino acid coded by the mutated codon is the same as the original. This is because there can be multiple codons that code for the same amino acid, so a substitution in the third position of a codon may not alter the resulting amino acid.