Predicting effects on protein length Which type of mutation, by definition, does not change the length (number of amino acids) of the encoded protein?

Introduction / Context:Different mutation classes have characteristic impacts on protein sequence and length. Distinguishing these outcomes aids in predicting phenotype and interpreting sequencing results in clinical and research settings.

Given Data / Assumptions:

• Nonsense mutations create premature stop codons, usually shortening proteins.
• Frameshifts alter the reading frame, almost always changing length and sequence downstream.
• Missense mutations substitute one amino acid for another without altering the total length.

Concept / Approach:A missense mutation is a base substitution that changes one codon to another coding for a different amino acid. Because the number of codons remains the same, the protein length is preserved. By contrast, nonsense and frameshift mutations typically affect length (shortened or altered-length products).

Step-by-Step Solution:Define each mutation type and its typical impact on length.Identify the class that leaves length unchanged: missense.Choose “Missense mutation.”

Verification / Alternative check:Protein domain analyses often tolerate certain missense changes with preserved length but altered function or stability, aligning with the definition.

Why Other Options Are Wrong:

• Nonsense: truncates the protein early.
• Frameshift: changes downstream codons and often introduces an early stop, altering length.
• “All of these”: incorrect because only missense preserves length.
• Splice-site deletion of an exon: changes length due to exon loss.

Common Pitfalls:Confusing “silent” (synonymous) with “missense”; both keep length, but silent does not change the amino acid while missense does.

Final Answer:Missense mutation.