Uses of Genetic Profiling

Section 1 of 6Where profiles are used

Parentage testing

• Parentage testing A profile can show whether a man is the biological father of a child, or less often whether a woman is the mother.
• A child may want to know who their father is, and what inherited conditions could run in the family.

Forensic investigations

• Forensic investigations Samples such as blood, saliva or hair left at a crime scene can be profiled and compared with suspects.
• Profiles can also identify bodies or remains that are too damaged to recognise.

Ruling people out

• Ruling people out A profile can show that a person was not the source of a sample, so innocent people can be cleared.

Section 2 of 6Working out parentage

1

Obtain DNA profiles from the mother, the child and the man (or men) who might be the father. All three types of profile are needed.

2

Look at each band in the child's profile. A child inherits half its DNA from each parent, so every band must come from one of them.

3

If the mother has the band, it could have come from her, and it tells you nothing about the father.

4

If the mother does not have the band, it must have come from the father, so any man lacking that band is ruled out.

5

The man whose profile contains all of the child's remaining bands is the likely father, and extra shared bands strengthen the conclusion.

Section 3 of 6Worked example: who is the father?

Child's band	In mother?	Men who have it	Conclusion
Band 1	Yes	Not needed	Inherited from mother; no information about the father
Band 2	No	B and D only	Men A and C are eliminated
Band 3	Yes	Not needed	Inherited from mother
Band 4	No	A, B and C	Man D lacks it, so D is eliminated; B is the only man left who has both band 2 and band 4
Band 6	No	B only	Supports B as the father

Section 4 of 6Forensic use of profiles

1Collect samples

• Collect samples Body fluids or hair are taken from the scene or victim, with care taken to avoid contamination.

2Profile the DNA

• Profile the DNA DNA is extracted, cut and separated to give a pattern of bands.

3Compare patterns

• Compare patterns The crime scene profile is compared with suspects, the victim and a control sample from people unconnected to the case.

4Draw a conclusion

• Draw a conclusion The suspect whose profile shares the most bands, or all bands, with the scene sample is the most likely source.

Section 5 of 6Key terms

Term	Meaning
Paternity	Being the biological father of a child.
Forensic	Using scientific methods to investigate crimes and provide evidence.
Control sample	A sample from a person unconnected to the case, used to check that the method is working and to compare.
Contamination	Unwanted DNA getting into a sample, which can give misleading results.
Band	A bar on a DNA profile showing a fragment of a particular size.

Section 6 of 6Exam technique

1

Using the father's profile on its own. The mother's profile is needed to decide which of the child's bands could not have come from her.

2

Eliminating a man because he lacks a band that the mother also has. Such a band could have been inherited from the mother.

3

Forgetting that a child's bands come from both parents, so every band must match one of them.

4

Ignoring contamination. A mixed sample can give a misleading profile, so samples must be collected carefully.