What describes a type of mutation that changes a single nucleotide?

• A. Deletion
• B. Insertion
• C. Point mutation
• D. Inversion

Answer: (C)

A single-base change in the DNA is called a point mutation. It involves substituting one nucleotide for another, which can alter a codon and potentially change the amino acid it encodes (missense), create a stop signal (nonsense), or still code for the same amino acid (silent). Point mutations affect the nucleotide itself but not the overall length of the sequence, unlike deletions (loss of bases) or insertions (added bases). Inversions, on the other hand, flip the orientation of a DNA segment, which changes the order rather than just a single base. Point mutations are a common type of DNA variation, often discussed in the context of SNPs when they occur in populations.