Genetic fingerprinting: method and uses
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Summary
Genetic fingerprinting: method and uses
In a nutshell
Genetic fingerprinting uses variable number tandem repeats (VNTRs) to create a unique fingerprint of an individual. These can then be compared and used to determine genetic relations, genetic variability and paternity.
Genetic fingerprinting
Approximately of human DNA is non-coding. These include variable number tandem repeats (VNTR), which are short sections of non-coding DNA that repeat over and over. They occur at various points throughout the genome. Every person will have a unique VNTR pattern, therefore, they can be used to create a genetic fingerprint to distinguish between individuals.
Note: Identical twins will have the same VNTRs as they have identical genomes.
Stage | Description | |
1. | Extraction | DNA is extracted from a sample. PCR can be used to amplify the DNA to ensure there is enough for visualisation. |
2. | Digestion | Restriction endonucleases are used to cleave DNA into fragments. |
3/4. | Separation | Gel electrophoresis is used to separate the fragments of DNA according to their relative size. They are then transferred onto a nylon membrane. |
5. | Hybridisation | Different tagged DNA probes that are complementary to the different VNTRs are used. Note: The DNA probes can be radioactively or fluorescently tagged. |
6/7. | Development | Light can be shone on to the membrane and the location of the VNTRs can be easily seen as this is where the fluorescently labelled probes bound. When using radioactive probes, the nylon membrane is placed on an x-ray film so the DNA fragments are exposed to the radiation. This creates bands where the radioactive DNA probes have bound to the VNTRs. |
Interpreting the genetic fingerprint
Two genetic fingerprints can be compared; if both fingerprints have bands (DNA fragment) at the same location, this means that they are a likely match. The results will be put in an automated scanning machine and it will return a result of the likelihood that the two DNA samples have come from the same person or from a relative.
Uses of genetic fingerprinting
Use | Description |
| Genetic relations | Genetic fingerprinting can be used during paternity testing as children inherit half of their DNA from each parent. Comparing the banding patterns of a child to their parents can establish whether a candidate is a parent of the child. |
Genetic variability | A population can be tested and compared to investigate the genetic variability within it. The closer the resemblance between the genetic fingerprints, the lower the genetic diversity. |
| Forensics | Genetic fingerprints are also used in forensic science. DNA samples, such as blood or semen, can be collected from crime scenes and a genetic fingerprint can be made. Another genetic fingerprint can be made from a suspect and these can be compared to ascertain the likelihood that the suspect committed the crime. |
| Medical diagnosis | Genetic fingerprinting can be used in medical diagnosis. ExampleHuntington's disease is a dominant inherited disorder that is caused by a repeated three base sequence (AGC) on chromosome four. It has been found that individual with fewer than repeats are unlikely to get the disease but those with more than repeats are at a much higher risk. |
| Breeding | Genetic fingerprinting can be used to establish how closely related two organisms are. This can therefore prevent inbreeding during breeding programmes in zoos. Plants and animals with desirable genes can be identified and bred to increase the likelihood of the desirable characteristic being passed on. |
FAQs - Frequently Asked Questions
What are VNTRs?
VNTRs are short sections of non-coding DNA that repeat over and over.
How is genetic fingerprinting used?
Genetic fingerprinting can be used during paternity testing as children inherit half of their DNA from each parent. Comparing the banding patterns of a child to their parents can establish whether a candidate is a parent of the child.
What is genetic fingerprinting?
Genetic fingerprinting uses variable number tandem repeats (VNTRs) to create a unique fingerprint of an individual.