DNA fingerprinting

DNA fingerprinting

1. DNA fingerprinting was invented in 1984 by Professor Sir Alec Jeffreys after he realised you could detect variations in human DNA, in the form of these minisatellites.

DNA fingerprinting is a technique that simultaneously detects lots of minisatellites in the genome to produce a pattern unique to an individual. This is a DNA fingerprint.

1. The probability of having two people with the same DNA fingerprint that are not identical twins is very small.

2. Just like your actual fingerprint, your DNA fingerprint is something you are born with, it is unique to you.

How was the first DNA fingerprint produced?

1. The first step of DNA fingerprinting was to extract DNA from a sample of human material, usually blood.

2. Molecular ‘scissors’, called restriction enzymes?, were used to cut the DNA. This resulted in thousands of pieces of DNA with a variety of different lengths.

3. These pieces of DNA were then separated according to size by a process called gel electrophoresis?:

The DNA was loaded into wells at one end of a porous gel, which acted a bit like a sieve.

An electric current was applied which pulled the negatively-charged DNA through the gel.

The shorter pieces of DNA moved through the gel easiest and therefore fastest. It is more difficult for the longer pieces of DNA to move through the gel so they travelled slower.

As a result, by the time the electric current was switched off, the DNA pieces had been separated in order of size. The smallest DNA molecules were furthest away from where the original sample was loaded on to the gel.