What are genetic mutations and their effects on proteins and phenotype; includes point mutations, insertions, deletions, and chromosomal changes.

• A. Point mutations always change the amino acid sequence.
• B. Insertions or deletions never affect reading frame.
• C. Insertions or deletions can cause frameshifts and alter protein function.
• D. Chromosomal changes occur only in noncoding regions.

Answer: (C)

Mutations change DNA sequences and can alter the protein built from that DNA, which in turn can affect an organism’s traits. A single base change may or may not change the amino acid due to the redundancy of the genetic code, so not all point mutations alter the protein. Inserting or deleting nucleotides changes the number of bases in a gene. If the number added or removed isn’t a multiple of three, the reading frame shifts, so every downstream codon is read differently. This typically produces a completely different sequence of amino acids and often a nonfunctional protein, leading to a phenotypic effect. Even when insertions or deletions are in multiples of three, they don’t shift the reading frame; they add or remove whole amino acids, which can still disrupt function depending on where they occur. Chromosomal changes involve larger-scale rearrangements and can affect coding regions as well as noncoding regions, not just noncoding DNA. So insertions or deletions can cause frameshifts and alter protein function, making that statement the best choice.