Pre lab Questions –
1. What sources of samples should be compared in a DNA forensic test ?
You should include the crime scene sample, and controls which include the victim, suspect and substrate
control
2. Why do you need to perform PCR on DNA obtained from a Crime Scene?
Because PCR is the only way to make enough copies of the sections (loci) of DNA that have the STRs
which have most of the differences among humans.
3. What might you see if you ran a DNA sample extracted from evidence on a gel before
PCR?
You wont be able to see any thing because there won’t be enough DNA.
4. What is a forensic DNA typing profile?
Is creating a profile of an individual STRs in several loci of their chromosomes. For the profile to be
individual it has to test 13 loci.
5. What is the difference between an allele and a locus?
An allele is one of the multiple possible STR found at a particular locus. Locus is the location of the
STR in a particular chromosome.
6. Why do forensic labs analyze non-coding DNA and not genes?
Because the non-coding regions are highly variable among humans. Genes are actually very similar
among people.
7. What components do you need to perform PCR?
You need DNA from a sample, the 2 primers that frame the STRs in a particular locus, nucleotides and
the polymerase enzyme.
8. Why does DNA move through an agarose gel in electrophoresis?
Because it is negatively charged. So it moves to the positive side through the gel.
9. What is an Allele Ladder? What is its function in DNA profiling?
Is the known possible STRs in the human population for a particular locus of a chromosome.
10. What is required to visualize DNA following electrophoresis?
It is necessary to dye it so the DNA STRs that have been separated become visible.