L20 Genetic Markers in Forensics

Question 1

Short tandem repeat loci

Answer 1

• consist of tandem repeats of a DNA motif of 1 to 6 bp
• also referred to as microsatellites
• widely used as genetic markers in population genetics and in forensics where neutrality is often assumed

Question 2

STRs in human disease

Answer 2

• can cause huntington disease, motor neuron disease and fragile X syndrome
• age of disease onset and/or severity of disease often depend on repeat length: longer is worse

Question 3

STR mutation

Answer 3

see onenote

• strand slippage
• stepwise mutation model
• mutation rates are highly variable across loci and can depend on may factors

Question 4

Typing STR loci using capillary gel electrophoresis

Answer 4

1. extraction of DNA
2. amplification via PCR
3. separation of PCR products (allele) according to length
4. detection via fluorescent dyes

Question 5

Some genotyping issues

Answer 5

see onenote

• microvariants
• silent/null alleles
• stutter
• pull-up peaks
• copy number variants

Question 6

Contamination

Answer 6

two sources of contamination:

1. by environmental DNA before the sample is collected
2. subsequent to sample collection e.g. in the lab

Question 7

How do we assess reliability of scientific evidence?

Answer 7

Can we evaluate the evidence in a way that is comprehensible to courts and not unfair to defendants?

Question 8

How do we assess reliability of scientific evidence?

Answer 8

Can we evaluate the evidence in a way that is comprehensible to courts and not unfair to defendants?