VNTRs and STRs are examples of which type?

• A. Single nucleotide polymorphisms.
• B. Tandem repeat polymorphisms.
• C. Copy number variations.
• D. Insertion-deletion polymorphisms.

Answer: (B)

VNTRs and STRs are examples of tandem repeat polymorphisms. They arise when a DNA motif is repeated in a row, and different individuals carry different numbers of these repeats at a given locus. The repeat unit for STRs is short (about 2–6 base pairs), while VNTRs use longer units (roughly 10–60 base pairs). This variation in repeat copy number makes these loci highly polymorphic and useful for sensitive genetic analyses such as forensic DNA profiling and linkage studies. They differ from SNPs, which are single-base changes; from copy number variations, which involve larger segments with variable copy numbers across the genome; and from insertion–deletion polymorphisms, which are about presence or absence of sequences rather than varying repeat counts.