Generating a DNA Profile

Question 1

What is the difference between sensitivity and discriminating power?

Answer 1

Sensitivity: the amount of starting material or the size of the stain we can begin working with.

Discriminating Power: Power to distinguish between one or another

Question 2

How much DNA was required to make a DNA profile?

Answer 2

• The DNA we leave behind in a fingerprint is roughly 100 cells and is plenty to generate a DNA profile.
• Most kits recommend that the starting material corresponds to the amount of DNA that you would get from as few as 100-200 cells.
• Each cells contain 6-7 pg of DNA, and DNA profiling kits generally recommend using 500-1000 picograms of template

Question 3

How much starting material does the DNA 17 Multiplex require?

Answer 3

• The DNA 17 multiplex is able to generate profiles with much less starting material.
• The DNA 17 requires about 80 cells (<500 picograms) for a standard result.

Question 4

What is a locus, and what is an allele?

Answer 4

• Locus (loci) is a specific location on a chromosome.
  
  • More simply, a specific spot we are paying attention to on the length of a person’s DNA molecules.
• Allele is a term used to describe a specific region of DNA which varies between people.
  
  • This can also be called a component
  • At each locus, we will see one (homozygous) or two (heterozygous) alleles.

Question 5

What is a Relative Fluorescent Unit?

Answer 5

RFUs are measures of the intensity of light picked up by the camera in the detector window, at different points in time.

• The vertical axis on the EPG identifies the RFUs
• The horizontal axis is measured in terms of minutes or seconds.

Question 6

What does the AMEL gene show?

Answer 6

• The Amelogenin gene resides on the X and Y chromosomes.
• If we have a profile with two peaks at the AMEL locus, the individual will have an X and Y chromosome and will be male.
• If we have a profile with one peak, the individual with be homozygous for X and will be female.

Question 7

How would one simply interpret an EPG?

Answer 7

1. One peak would equal homozygous at a particular locus
2. Two peaks would indicate heterozygous at a particular locus
3. Three or more may indicate a mixed sample.
4. Peaks on the left hand side = smallest fragments. Larger fragments will appear on the right hand side.
5. Peak height is proportional to the amount of DNA that gave rise to that particular peak.