How do mutations affect proteins?

• A. Mutations can alter the amino acid sequence of proteins, potentially affecting their function.
• B. Mutations always increase protein activity.
• C. Mutations decrease mRNA stability but not protein.
• D. Mutations only affect RNA, not protein

Answer: (A)

Mutations can change the blueprint that makes proteins, which can alter the amino acid sequence of the protein and thus its behavior. The sequence of amino acids determines how a protein folds into its three‑dimensional shape, where it binds to other molecules, and how stable or flexible it is. When a mutation changes one codon, several things can happen:

• A different amino acid (missense) may alter charge, size, or chemical properties at a crucial spot, potentially distorting the active site or folding and changing function—often reducing it, sometimes having little effect, and rarely enhancing it.

• A stop codon can be created early (nonsense), producing a truncated protein that is usually nonfunctional and sometimes degraded quickly.

• A shift in the reading frame from insertions or deletions (frameshift) can completely change downstream amino acids, typically wrecking structure and function.

• A DNA change that does not alter the amino acid sequence (silent) usually has no effect on the protein itself, though it can affect how efficiently a protein is produced or how it’s spliced in the RNA.

It’s also possible for mutations to affect how much protein is made or how it’s processed in the cell, but the central idea is that changing the amino acid sequence can directly influence protein structure and function. That’s why the statement about mutations altering the amino acid sequence and potentially affecting function is the best description.