Explain how Variable Number Tandem Repeat (VNTR) analysis is used for DNA fingerprinting and give an example of a situation where it is applied.
Answer
VNTRs are DNA loci that contain short sequence repeats; the number of repeats varies among individuals. PCR amplifies these loci, and gel electrophoresis separates the fragments according to length. The resulting pattern of fragment sizes forms a DNA fingerprint that can be compared between samples. This technique is routinely used in forensic investigations to identify suspects and in paternity testing to confirm parentage.
Step-by-step solution
- Identify VNTR loci that show high inter‑individual variability.
- Design primers flanking the repeat region and perform PCR amplification.
- Separate the PCR products on an agarose gel and detect band sizes.
- Construct a band‑size profile (fingerprint) for each sample.
- Compare fingerprints to determine identity or relatedness.
- Example application: determining whether a suspect’s DNA matches DNA found at a crime scene.
Common mistake: Confusing VNTR with STR or neglecting to use PCR amplification
Concept tested: DNA fingerprinting with VNTRs
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