In genetics, a single-nucleotide polymorphism (SNP) most commonly results from which type of mutation?

• A. A deletion of an entire exon due to unequal crossing over
• B. A base substitution (point mutation) changing one nucleotide to another
• C. A chromosomal inversion that reverses the orientation of a DNA segment
• D. An insertion of one or more nucleotides that shifts the reading frame (frameshift mutation)

Answer: (B)

Verified step by step guidance

1. Understand what a single-nucleotide polymorphism (SNP) is: it is a variation at a single position in a DNA sequence among individuals.
2. Recall the types of mutations that can occur in DNA: base substitutions (point mutations), insertions, deletions, inversions, and larger chromosomal rearrangements.
3. Recognize that SNPs specifically involve changes at a single nucleotide position, which corresponds to a base substitution where one nucleotide is replaced by another.
4. Differentiate SNPs from other mutations such as deletions of entire exons, chromosomal inversions, or frameshift mutations caused by insertions or deletions, which affect larger DNA segments or reading frames.
5. Conclude that the mutation type most commonly resulting in an SNP is a base substitution (point mutation) changing one nucleotide to another.