Which statement best describes a frameshift mutation?

• A. A single-nucleotide substitution that changes one amino acid but does not alter the reading frame (missense mutation)
• B. A mutation in which a DNA segment is reversed in orientation within the chromosome (inversion)
• C. A point mutation that converts a sense codon into a stop codon, prematurely terminating translation (nonsense mutation)
• D. An insertion or deletion of nucleotides not in multiples of three that shifts the mRNA codon reading frame, often altering all downstream amino acids

Answer: (D)