EXAM 3: ch.10/11 DNA degradation and LCN

Question 1

Discuss advantages and disadvantages of
miniSTR assays.

Answer 1

CHECK

adv. - (moving PCR primers)- you can identify degraded DNA,
dis.- you can only test for 8 loci

Question 2

Name at least two ways that the presence of a
mixture can be detected.

Answer 2

• stutter appears abnormally high
  *severe peak height imbalance

Question 3

What are the causes of allele drop-in and allele
drop-out in the context of amplifying low
amounts of DNA template?

Answer 3

CHECK

LCN ; allele drop in means you have such small quantities you have small limits so low DNA is amplified
not enough , so one allele may not be amplified

Question 4

how does DNA degradation happen?

Answer 4

water,oxygen, nucleases, UV radiation

Question 5

who uses degraded DNA

Answer 5

miniSTR/ SNPs

Question 6

what significant event used miniSTR

Answer 6

WTC identification

Question 7

disadvantages of miniSTR

Answer 7

few loci can be multiplexed

Question 8

decay curve is seen …

Answer 8

degraded DNA

Question 9

DNA degradation means less

Answer 9

Loci work (lower peak heights & loss of alleles)

Question 10

true or false: with degraded DNA samples information is simply lost at the larger sized STR loci

Answer 10

true

Question 11

DNA profiles are essentially a pair of numbers..

Answer 11

if DNA was damaged then the string of numbers is shorter and less informative

Question 12

Low copy number (LCN) comes from..

Answer 12

low profile touch DNA samples

Question 13

where can you get touch DNA from

Answer 13

fingerprint residues or secondary transfer (skin cells)

Question 14

what are some precautions for using LCN

Answer 14

• at least 2 amplifications from the same DNA extract
  -sterile environment
  -elimination database

Question 15

what are some issues with LCN?

Answer 15

• allele dropout
• stutter peaks enhanced
  -peak height imbalance
  -sporadic contamination

Question 16

3 ways to indicate if something is a mixture :

Answer 16

1. do any of the loci show more than 2 peaks
2. is there a severe peak height imbalance
3. does the stutter product appear abnormally high

Question 17

how do mixtures arise ?

Answer 17

when two or more individuals contribute to the sample being tested

Question 18

when can mixtures be hard to detect ?

Answer 18

degraded DNA

Question 19

what process (learned previously) can help distinguish male and female components

Answer 19

differential extraction (with the help of Y chromosome markers)

Question 20

6 steps in interpreting a mixture

Answer 20

1. Identify presence of mixture
2. Designate allele peaks
3. Identify number of potential contributors
4. Estimate relative ratio of individuals in mixture
5. Consider all possible genotype combinations
6. Compare reference samples