8.4.10 Variable Number Tandem Repeats

Variable Number Tandem Repeats (VNTRs)

VNTRs are short repeating sequences of DNA bases located in non-coding regions of the genome. The number of repeats at a specific locus varies greatly between individuals, making them useful for identifying genetic differences.

Genetic Fingerprinting

Genetic fingerprinting is a technique that uses VNTRs to identify genetic variation between individuals. It is based on the fact that the likelihood of two unrelated individuals having identical VNTR patterns is extremely low.

Process of Genetic Fingerprinting

1. DNA Extraction:

• DNA is isolated from a sample (e.g. blood, saliva, or hair).

2. Amplification:

• PCR (polymerase chain reaction) is used to amplify the VNTR regions.

3. Cutting DNA:

• Restriction enzymes are used to cut DNA at specific sites around the VNTRs.

4. Separation of Fragments:

• DNA fragments are separated by size using gel electrophoresis.
• Smaller fragments move further through the gel.

5. Visualisation:

• A radioactive probe or fluorescent dye binds to the VNTR regions, allowing them to be visualised as bands on the gel.

6. Comparison:

• The banding pattern (the genetic fingerprint) is unique to each individual and can be compared across samples.

Applications of Genetic Fingerprinting

1. Forensic Science:

• Used to match crime scene evidence (e.g. blood or hair) to suspects.

2. Paternity Testing:

• Determines biological relationships by comparing VNTR patterns of the child and potential parents.

3. Identifying Genetic Relationships:

• Used to study genetic diversity and evolutionary relationships in populations.

4. Medical Diagnosis:

• Identifies individuals at risk for inherited diseases by comparing genetic markers.

5. Wildlife Conservation:

• Tracks genetic diversity in endangered species to aid breeding programmes.