What is a point mutation?

• A. A mutation involving a large segment of DNA
• B. A change in a single base pair in DNA
• C. A mutation resulting in a loss of a chromosome
• D. A mutation that adds extra chromosomes

Answer: (B)

A point mutation refers to a change in a single base pair within the DNA sequence. This can occur through various mechanisms, such as the substitution of one nucleotide for another (which can result in a missense, nonsense, or silent mutation), or through small insertions or deletions of nucleotides. Because point mutations can alter the amino acid sequence of a protein, they can have significant effects on an organism's phenotype and function, especially if they occur within coding regions of genes or regulatory elements.

In contrast, other types of mutations involve larger segments of DNA or more substantial chromosomal alterations, such as deletions, duplications, or entire chromosome gains or losses, which are not classified as point mutations. The specificity of a point mutation to a single nucleotide change makes it a fundamental concept in genetics, particularly in the study of genetic diseases and molecular evolution.