DNA fingerprinting Flashcards
Role of DNA fingerprinting
Methods used to identify an individual from a sample of DNA by looking at unique pattern in DNA
Method which relies on the unique pattern made by a series of DNA fragment after separating them according to their length by gel electrophoresis
History
1984 by Sir Jeffery which he realised he could detect variations in human DNA
Comparison
PCR in terms of forensic application criminals etc
A piece of x-ray filmed exposed to fragments ,r adioactive probe had become attached .
Pattern would be analysed - Lead to investigation
Procedure - Ecstacy
Extraction of DNA:
From cell /tissue of muscle , semen , saliva or blood
Blood is being treated with a series of chemicals until pure DNA emerges as a white solid
DNA stored , dissolved in water and fridge .
Cutting up the DNA using an enzyme
Involves using restriction enzyme
Using colourless liquid to the DNA with another colourless liquid
Enzyme take quite some to cut all places in the strands
Separating DNA fragments on the gel
Separates the different sizes of the DNA fragment generated by cutting up the DNA.
Observe the small fragments move faster than larger ones , so DNA fragments are separated as they move in the gel .
Transferring DNA on paper
gel separated onto white nitrocellulose paper , so paper carries an extract replica of DNA on the gel .
Adding the radioactive probe
Probe sticks to the fragments of the DNA that has matching sequence , but only those fragments that have matching sequence of letters , no other fragments
Setting up X- ray film
Dark mode , nitrocellulose paper placed against a piece of x-ray film
X- ray film records pattern of radioactivity on the paper , probe has struck .
Pattern of DNA fragment see where probes stuck