Genetic profiling

In the human genome there is a small amount of DNA that is unique to individuals.

By cutting a sample of DNA into fragments using enzymes it is possible to make a characteristic profile of DNA bands for individuals. This technique is called DNA profiling, and is a technique used to determine paternity, and can help solve crimes where the suspect may have left a sample of body tissue at the crime scene. It can also be used in other organisms to compare different species for classification purposes.

Using DNA profiling in solving crimes

Diagram showing how DNA profiling is used to solve cases

DNA is often left at the scene of a crime, it is found in blood, skin even hair. Once the DNA has been isolated from the victim and if suspects are identified then DNA profiling can be useful in placing a suspect at the scene of the crime.

Question

In the example above, which suspect has left their DNA at the crime scene?

Suspect 1, the bands of DNA in their profile match the bands of the DNA profile found at the crime scene.

Using DNA profiles to determine paternity

Diagram showing how DNA profiles can be used to determine paternity

To determine paternity, the baby's and its mother's DNA profile must be known. Any band that can be seen in the baby's DNA that cannot be attributed as coming from its mother must be found in the DNA of the father or paternity cannot be confirmed.

Question

In the example above, is father 1 or 2 the father of the baby?

Father 1

The baby's DNA band 4 is not found in the mother's profile and only father 1 possesses the same band. This also true of band 8.

DNA profiles can also be used to identify alleles associated with particular genetic disorders. Neonatal testing carries out this process to look for disorders such as Cystic fibrosis. The early identification of this and other genetic disorders results in early treatment which can reduce the impact of the disorder on the life of the sufferer.

Genetic profiling can be controversial. The table below summarises some of the advantages and disadvantages of using this technique.

AdvantagesDisadvantages
DNA evidence is reliable as it is highly unlikely that two people would share the same profile, except in the case of identical twinsSome people are concerned that DNA could potentially be used by insurance companies or employers used to discriminate against people with genetic conditions
DNA profiles can be used to determine paternityStorage of DNA profiles can be seen as an invasion of privacy
DNA profiles can be used to identify genetic disorders earlyTheft of DNA profiles from a database is a threat
DNA profiles can be used to place suspects at a crime sceneIt is possible to plant DNA at a crime scene giving false evidence or an innocent persons DNA might be at the scene even though they had nothing to do with the crime