16.8 Genetic Fingerprinting

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95% of a humans DNA is made of introns, and these make up core sequences. These sequences are different in all human except for identical twins.

Each sequence will still come from one parent.

Genetic fingerprinting is made up of 6 stages:

Stage 1:

Extraction- A small amount of DNA is extracted from the individuals blood and then copied through the PCR method.

Stage 2:

Digestion- This is then cut into fragments by restriction endonuclease.

Stage 3:

Separation- Gel electropherosis is used to split the fragments in order of size. The fragments are then immersed in alkali in order to split them into single strands

Separation 2- A nylon membrane is then placed over the gel with absorbent sheets attached behind it. The liquid is drawn up via capillary action. Ultraviolet rays are used to fix the DNA fragments onto the membrane. They will be in the exact same positions as they were on the gel.

Stage 4:

Hybridisation- DNA probes are used to join to the fragments. Specific temperatures and PH's must be made for the process to work effectively. Many probes are used, each binding to different core sequences.


claire hopkins


what is capillary action? :)


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