Question

a mutation causes a sequence of dna that has the nucleotides ttg to be changed to tcg. the resulting protein has a different sequence of amino acids. which type of mutation is this?
○ missense
○ nonsense
○ silent
○ frameshift

Explanation:

1. First, recall the definitions of each mutation type:

• Missense mutation: A single nucleotide change (point mutation) that results in a different amino acid being coded for.
• Nonsense mutation: A point mutation that results in a premature stop codon, truncating the protein.
• Silent mutation: A point mutation that does not change the amino acid coded for (due to the redundancy of the genetic code).
• Frameshift mutation: Insertion or deletion of nucleotides (not in multiples of 3) that shifts the reading frame, altering all subsequent codons.

1. In the given problem, the DNA sequence changes from TTG to TCG (a single nucleotide change, a point mutation). The resulting protein has a different amino acid sequence, which fits the definition of a missense mutation. It is not a nonsense mutation (no stop codon introduced), not silent (amino acid changed), and not frameshift (no insertion/deletion, just a single base change).

Answer:

A. missense