Which mutation changes the reading frame of the mRNA, resulting in a new protein product?

Which mutation changes the reading frame of the mRNA, resulting in a new protein product?

• A. Missense mutations
• B. Frameshift mutation
• C. Nonsense mutations
• D. Inversion mutation

Answer: (B)

Frameshift mutations change the reading frame of the mRNA by inserting or deleting nucleotides in a way that shifts the grouping of codons. Because the ribosome reads three bases at a time, any shift causes every downstream codon to be read differently, producing a new sequence of amino acids and often an early stop, which typically yields a nonfunctional protein. A change that only swaps one codon for another alters a single amino acid but does not shift the downstream reading frame. A change that converts a codon to a stop truncates the protein but keeps the reading frame intact. An inversion is a larger chromosomal rearrangement that flips a segment of DNA and is not defined by stepping the reading frame of mRNA in this way.

Frameshift mutations change the reading frame of the mRNA by inserting or deleting nucleotides in a way that shifts the grouping of codons. Because the ribosome reads three bases at a time, any shift causes every downstream codon to be read differently, producing a new sequence of amino acids and often an early stop, which typically yields a nonfunctional protein.

A change that only swaps one codon for another alters a single amino acid but does not shift the downstream reading frame. A change that converts a codon to a stop truncates the protein but keeps the reading frame intact. An inversion is a larger chromosomal rearrangement that flips a segment of DNA and is not defined by stepping the reading frame of mRNA in this way.