You would use restriction enzymes first. These cut long DNA strands into smaller DNA fragments. These are then amplified via PCR. The gel electrophoresis gives bands, each of which containing these smaller fragments.
I'm doing the exam for Topic 5 and 6 next week but am a little confused about something.
When making a DNA profile what is the process?
I know it is PCR then gel electrophoresis but where do the restriction enzymes (mentioned bottom of p.75) come in? What order does it all take place?
Oh, and DNA profiling is the process of obtaining the DNA, creating the fragments, and multiplying these fragments using a PCR machine, seperating these fragments and visualising the fragments using the method of gel electrophoresis.... this is to compare a DNA with a suspects DNA... and this highlights the STRs of the suspects and the ones you are comparing it to...
Oh, and DNA profiling is the process of obtaining the DNA, creating the fragments, and multiplying these fragments using a PCR machine, seperating these fragments and visualising the fragments using the method of gel electrophoresis.... this is to compare a DNA with a suspects DNA... and this highlights the STRs of the suspects and the ones you are comparing it to...
Right so the DNA is extracted etc., the STR fragments are cut using restriction enzymes, then placed in the PCR to be amplified before gel electrophoresis?
In the diagram though on p.77 they've put the DNA sample into the PCR but I can't see any restriction enzymes anywhere. Can you just amplify it then or could you use PCR or restriction enzymes?
(Sorry if I sound stupid, this has confused me all year)
Right so the DNA is extracted etc., the STR fragments are cut using restriction enzymes, then placed in the PCR to be amplified before gel electrophoresis?
Yes! Gel electrophoresis is the final step, where you analyse the different fragments and see if the original DNA matches any of the suspects..
In the diagram though on p.77 they've put the DNA sample into the PCR but I can't see any restriction enzymes anywhere. Can you just amplify it then or could you use PCR or restriction enzymes?
(Sorry if I sound stupid, this has confused me all year)
There wouldn't be any restriction enzymes there because:
a) Restriction enzymes are used to cut up the DNA fragments before amplying the DNA sample.
b) In that diagram, it is showing you the cycle of PCR. This is the process of making a lot of copies of the DNA sample, so you wouldn't need restriction enzymes in this process..