What is the first step in obtaining a DNA fingerprint?

Answer 1

The collection and processing of DNA evidence and the collection and processing of latent fingerprint evidence are two entirely separate and distinct procedures and are not in any way connected to one another.

Answer 2

I will use an example to illistrate the process. Imagine we are trying to investigate a crime scene and we have found a suspect, from the crime scene we have obtained a blood sample, we have already run genetic fingerprinting on this sample. We can then look at the banding patterns of this sample of blood and compare them to that of the suspect, if the banding patterns match, we can be confident that the suspect is guilty.

Firstly we need to extract the DNA. As the sample obtained from the crime scene is likely to be small, the polymerase chain reaction is carried out to amplify the sample.

Next is digestion, here were use a series of restriction endonuclease enzymes which will cut the DNA close to specific core sequences in the DNA ( repetitive sequences in the non-coding sections of DNA called introns). This will result in different length DNA fragments.

The next stage is separation, this is where we use gel electrophoresis. These DNA fragments are placed onto a viscous agar gel. Electrodes are turned on, the DNA fragments are negatively charged and so will move towards the anode. The smallest fragments will move the furthest as they have the less resistence to the gel. The second half of separation is called southern blotting. This entails an alkali solution being poured onto the gel, to separate the double strands of DNA. A nylon membrane and absorbant sheets are then placed over the gel, so that the nylon membrane absorbs the DNA fragments by capillary action, at exactly the same posistion. UV light is then used to anneal these fragments to the membrane. The next stage is hybridisation, this is where radioactive probes are poured over the fragments, these probes are complementary to the core sequences of the fragment.

Next an X-ray film is placed over the nylon membrane and the banding patterns are exposed due to the radioactive probes.

The banding patterns from this suspect, can be compared to the banding patterns of the blood sample and then we can see whether we have a match.

Answer 3

DNA fingerprinting, also refered to as genetic fingerprinting is obtained from blood samples, semen, saliva and other bodily fluids.

Answer 4

Odiously blood

Answer 5

Foos