Identifying a Body Flashcards
Describe first stage in DNA profiling
- after DNA extracted, it is amplified by
Polymerase chain reaction
1) denaturation - heated at 95C to break H bonds between bases
2) annealing - cooled to 50-60C for primers to anneal to ends of strands of DNA
3) extension - heated back to 72°C (optimum for Taq polymerase), Taq polymerase build complimentary DNA strand to create copy - repeated to create many copies
Describe second stage of DNA profiling
Gel electrophoresis
- separates fragments according to size on agarose gel
1) fragments added to wells of an agarose gel
2) current passed through gel; as DNA is negatively charged, moves from neg to pos
3) smaller fragments travel faster, so move further down gel in same amount of time
4) Southern blogging or UV tagging makes bonding visible
What are used of DNA profiling?
Paternity tests, determining ancestry, criminal cases, evolutionary links
How can results of gel electrophoresis be analysed?
Produces pattern of bands on gel representing DNA fragments of different length cut using restriction enzymes after PCR –> cut DNA at specific locatio s so always cut in sections of repeated bases (variable number tandem repeats), different ppl have different number of repeats on these regions so fragments will differ
