Free DNA Profiling OCR A Level Biology revision notes – covering specification point 6.1.3(c).
DNA profiling* is a technique that produces a banding pattern from DNA fragments of the individual’s genome known as a DNA profile**.
*Also known as genetic fingerprinting.
**Also known as a genetic fingerprint.
DNA Profiling: Method
DNA profiling uses PCR to amplify a sample of DNA, and gel electrophoresis to separate out the STRs based on their size.
The process of DNA profiling can be summarised as:
- A DNA sample is obtained from the individual (e.g. mouth swab, blood).
- If the sample is small, the DNA is amplified by PCR to produce sufficient quantities.
- The DNA is digested with restriction enzymes, which cut it at specific recognition sites* into fragments that vary in length between individuals.
- The fragments are separated by gel electrophoresis according to their length, producing a pattern of bands.
- The agarose gel is stained to make the bands of DNA visible.
- The banding patterns of the samples are compared to identify matching bands.
*Also known as recognition sequences in reference to the DNA sequence that the restriction enzyme binds to.
Uses of DNA Profiling
DNA profiling is used in forensic science, determining relatedness, and analysing the risk of disease:
- Forensic science uses DNA profiles to determine if an individual is a match for a biological sample obtained from a crime scene.
- Determining relatedness is when the DNA profiles of individuals are used to establish if they are biologically related (e.g. paternity testing).
- Analysis of disease risk may involve identifying DNA sequences, mutations, or STRs linked with disease-associated alleles.