Background Biology
DNA Fingerprinting
13 steps of background science. Read them in order, or jump to a step that you need.
The technique for DNA fingerprinting models a more complex technique that is performed on human DNA samples. The enzyme mixture contains two restriction endonucleases called EcoRI and PstI. These enzymes recognise specific sequences (called… The restriction enzyme will cut the DNA strand wherever it finds the specific sequence it cuts at. DNA fragments of different lengths are… If the DNA is different the restriction enzymes will cut in different places, creating DNA fragments of different lengths. If the DNA is the… We can analyse DNA fragments of different lengths using gel electrophoresis (which literally means carry with electricity). A porous agarose gel is placed in a chamber filled with a conductive buffer. In gel electrophoresis, each DNA sample (that has been cut using restriction enzymes) is placed into a well in the agarose gel. The DNA is… An electrical current is passed through the gel, as DNA is negatively charged, the fragments of DNA are drawn towards the positive pole. The porous agarose gel acts a bit like a sieve. The smaller DNA fragments can move more easily through it than the larger DNA fragments. So… Once the gel is run it is still not possible to see the DNA bands until you have stained the DNA. Once the DNA is stained it is possible to analyse the banding pattern for each of the suspects and compare them to the banding pattern… In this example shown here suspect 2 would be the murderer, as the banding pattern formed by that DNA sample exactly matches that of the DNA… It should be noted that although this DNA evidence can say that suspect 2 was at the crime scene, other evidence may be needed to prove…