Dna for Forensics
5/12/12 11-12am PS318 Dr Nandini Hayes Note-taker Zia
Last week – we talked about PCR and how important it is in the forensic setting. We will finish off talking about PCR, and then we will discuss how it can be used.
If we go back to the slide of the double stranded DNA, and if we take that to a high temperature, the two strands separate, you then add the primers, which interact with ? On the strand, synthesis takes place in the 5-3 direction, then you end up with 2 molecules identical to the DNA, and then you do another round, so it's an exponential increase.
There are different enzymes and polymerases, which come from bacteria and hot springs. The original polymerase is the taq polymerase. In the forensic setting the copying is extremely important. Now there are vent? Polymerases, which are much more efficient and effective, known for its proof reading, when bases are incorporates you can get errors, with the incorrect base being put in. It will happen 1 in every thousand. If you feed in an enzyme that will release the process to reach the enzyme going in from the 3-5 strand, to take away the base; and put in the correct base.
Some enzymes do less better than others. You get your standard taq, then add a small amount of higher fidelity polymerases, so you can remove the incorrect base and insert the correct one.
Visualising the process of PCR (See Moodle)
In laboratories without a high through point of PCR, reactions will usually happen using a gel 'agrose' (See Moodle) it looks like jelly. You can make slabs of this gel. You boil up the agrose which melts, then you cast it in a square cast, so you have a slab of jelly. You can then put in wells and holes into the slabs. To put in your samples, place gel on piece of equipment, and then you can run electrical currents through. When you put electric through you have a complete current.
DNA is it positive or negative? It is negative. If you put a current through it, it will move towards the
Last week – we talked about PCR and how important it is in the forensic setting. We will finish off talking about PCR, and then we will discuss how it can be used.
If we go back to the slide of the double stranded DNA, and if we take that to a high temperature, the two strands separate, you then add the primers, which interact with ? On the strand, synthesis takes place in the 5-3 direction, then you end up with 2 molecules identical to the DNA, and then you do another round, so it's an exponential increase.
There are different enzymes and polymerases, which come from bacteria and hot springs. The original polymerase is the taq polymerase. In the forensic setting the copying is extremely important. Now there are vent? Polymerases, which are much more efficient and effective, known for its proof reading, when bases are incorporates you can get errors, with the incorrect base being put in. It will happen 1 in every thousand. If you feed in an enzyme that will release the process to reach the enzyme going in from the 3-5 strand, to take away the base; and put in the correct base.
Some enzymes do less better than others. You get your standard taq, then add a small amount of higher fidelity polymerases, so you can remove the incorrect base and insert the correct one.
Visualising the process of PCR (See Moodle)
In laboratories without a high through point of PCR, reactions will usually happen using a gel 'agrose' (See Moodle) it looks like jelly. You can make slabs of this gel. You boil up the agrose which melts, then you cast it in a square cast, so you have a slab of jelly. You can then put in wells and holes into the slabs. To put in your samples, place gel on piece of equipment, and then you can run electrical currents through. When you put electric through you have a complete current.
DNA is it positive or negative? It is negative. If you put a current through it, it will move towards the