visualising the fragments/ using the dna profile - lqc 2a Flashcards
Simply describe the techniques used to visualise the fragments
Southern blotting – STR DNA fragments are transferred to a nylon or nitrocellulose membrane. Membrane then incubated with a DNA probe which complementary base pairs to the STR fragments (hybridisation). The probe may be radioactive (P32) or fluorescently tagged to aid visualisation.
Fluorescent primers in PCR remain attached to the DNA after the last cycle and pass down the gel to be detected and analysed by a computer.
state the possible uses of dna profiling
Identifying victims and potential criminals. Settling paternity disputes. Identifying stolen animals. Confirming pedigree lineage in racehorses, dogs and farm animals. Confirming foodstuffs i.e. rice, meat. Identifying evolutionary relationships and species. Checking variation within species.
how is a conclusion reached from the profile
Each STR fragment shows up as a band on the gel. Compare the bands in the test sample and the reference sample i.e. from a hairbrush. A match is confirmed if the same number of bands are seen in exactly the same positions.
describe why is dna profiling not infallible (never wrong)
The profiling procedure has many steps where cross contamination could occur. Only some (10) STR sequences are analysed and not the entire DNA sequence of an individual. There is a chance that another individual has an identical profile. Closely related individuals could have identical profiles. However the chance is in excess of 1 billion!
