DNA Fingerprinting

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DNA Profiling

(DNA fingerprinting)

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What is DNA Profiling?

A technique used by scientists to distinguish between individuals of the same species using only samples of their DNA

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Who Invented it?

The process of DNA fingerprinting was invented by Alec Jeffreys at the University of Leicester in 1985.

He was knighted in 1994.

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Stages of DNA Profiling

Stage 1:

Cells are broken down

to release DNA

If only a small amount of DNA is available it can be amplified using the polymerase chain reaction (PCR)

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Stages of DNA Profiling

Step 2:

The DNA is cut into fragments using restriction enzymes.

Each restriction enzyme cuts DNA at a specific base sequence.

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Stages of DNA Profiling

The sections of DNA that are cut out are called restriction fragments.

This yields thousands of restriction fragments of all different sizes because the base sequences being cut may be far apart (long fragment) or close together (short fragment).

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Stages of DNA Profiling

Stage 3:

Fragments are separated on the basis of size using a process called gel electrophoresis.

DNA fragments are injected into wells and an electric current is applied along the gel.

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Stages of DNA Profiling

DNA is negatively charged so it is attracted to the positive end of the gel.

The shorter DNA fragments move faster than the longer fragments.

DNA is separated on basis of size.

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Stages of DNA Profiling

A radioactive material is added which combines with the DNA fragments to produce a fluorescent image.

A photographic copy of the DNA bands is obtained.

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Stages of DNA Profiling

Stage 4:

The pattern of fragment distribution is then analysed.

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Uses of DNA Profiling

DNA profiling is used to solve crimes and medical problems

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Crime