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Techniques Used in Biotechnology

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Restriction Fragment Length polymorphism: DNA fragments cut by enzymes specific to a base sequence (restriction enzymes) generating a DNA fragment whose size varies from one individual to another (except for identical twins). Used as markers on genome maps and for screening mutations and genetic diseases.   In the case of police investigation (forensic science), it is referred as DNA fingerprint.

Restriction enzymes: these enzymes are made from bacteria and cut pieces of DNA at specific base sequence.

Nucleotides: The building block of a DNA. The gene is stored as a code made up of the four nucleotides running along the length of each strand and joined together in pairs. Nucleotides are made up of 4 bases known as Adenine (A), Guanine (G), Thymine (T) and Cytosine (C).

Sequence: when the nucleotides are linked together into a chain.

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DNA is extracted from a sample (in this case- blood) by a special method.  Click here to find out about DNA extraction. Once extracted, DNA is cut with restriction enzymes and, a method called Southern Blot is carried out: 

Southern Blot: cut DNA is run on a special apparatus, called gel electrophoresis that separates the DNA fragments by size: the smaller the fragment is, the further down it will go on the gel.

When electrophoresis is done, the gel is transferred to a special nylon filter where the cut DNA becomes single stranded and is transferred to the filter. The filter is then mixed with a probe (a specific piece of gene) that has been radioactively labeled.  This will allow the probe to bind to the matching DNA sequence in the filter. The filter is then placed with an X-ray film. The radioactivity from the probe exposes the film, showing where it bound in the DNA. Click here to see an image of Southern blot.


Learn about PCR technique.

Learn about Sequencing technique.



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