Which statement differentiates VNTRs from STRs regarding length?

• A. STRs are longer than VNTRs
• B. VNTRs are longer sequences of repeated DNA
• C. They are the same length
• D. VNTRs are shorter

Answer: (B)

The key idea is that VNTRs and STRs differ in the size of their repeating units, which affects the overall length of the repeated DNA. VNTRs (Variable Number Tandem Repeats) have longer repeat units, typically 7 to 100 base pairs, and the total length of a VNTR allele grows with the number of repeats. This can produce fairly long DNA fragments, often hundreds to thousands of base pairs. STRs (Short Tandem Repeats) use very short repeat units, usually 2 to 6 base pairs, leading to much shorter alleles and fragments.

So, VNTRs are longer sequences of repeated DNA, which is why that statement is the correct distinction in terms of length. The other options describe STRs as longer or equal, or say VNTRs are shorter, which doesn’t fit how these markers are defined.