Question

Which point mutation changes a codon but does not alter the resulting amino acid?

• A. Missense mutation
• B. Nonsense mutation
• C. Silent mutation
• D. Frameshift mutation

Hint:

Silent mutation = \textbf{No change in protein}. Think: Different codon, same amino acid.

Answer 1

The Correct Option is C

Concept: A point mutation is a change in a single nucleotide in the DNA sequence. Depending on its effect on the encoded protein, point mutations are classified as:

• Silent mutation: Changes the codon but not the amino acid due to redundancy of the genetic code.
• Missense mutation: Changes the codon, resulting in a different amino acid.
• Nonsense mutation: Converts a codon into a stop codon, terminating protein synthesis.
• Frameshift mutation: Caused by insertion/deletion, altering the reading frame.

The genetic code is degenerate, meaning multiple codons can code for the same amino acid.
Step 1: Understand codon redundancy.
For example, the codons UUU and UUC both code for phenylalanine. A mutation from UUU to UUC changes the codon but not the amino acid.
Step 2: Identify the mutation type.
Such mutations that do not affect the amino acid sequence are called silent mutations.
Step 3: Eliminate other options.

• Missense changes amino acid.
• Nonsense creates stop codon.
• Frameshift alters entire reading frame.

Step 4: Conclude the answer.
Thus, the correct answer is silent mutation.