What type of mutation involves changes in one or a few nucleotides?

• A. Point mutation
• B. Frameshift mutation
• C. Chromosomal mutation
• D. Silent mutation

Answer: (A)

Changes in DNA at a single nucleotide or a few nucleotides are called point mutations. This category describes small-scale changes, which can alter a codon and lead to a different amino acid (missense), create a premature stop (nonsense), or, if the codon still codes for the same amino acid, produce a silent mutation. The key idea is the limited size of the change. In contrast, a frameshift mutation happens when nucleotides are inserted or deleted in numbers not divisible by three, shifting every downstream codon and usually wrecking the entire protein sequence. Larger-scale changes affecting whole chromosome segments are chromosomal mutations, while the silent mutation is a type of point mutation where the amino acid remains unchanged due to the genetic code’s redundancy. So, the best term for changes in one or a few nucleotides is point mutation.