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Lecture 21 – Disadvantages of mtDNA

Course Code
ANTH 2235A/B
Eldon Molto

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Lecture 21 Disadvantages of mtDNA
The high copy number and the sensitivity of PCR makes it more susceptible
to contamination (must have clean lab facility for mtDNA analysis (=very
costly to construct lab and to pay for case (~$1500-2000 American)
Can’t discriminate maternal relatives, in small areas with high degree of
endogamy this could be problematic
Low probative value (usually 1/100 to 1/1000) depending on size of
New to courts (voir dire in Canada 1999) = more acrimony and less
Possibility of heteroplasmy (two profiles at a locus in one individual)
Difficult to quantify
Contamination Control
o Protective clothing is worn in the field when possible and only a
designated person collects samples
o All field and lab personnel should have their profile on record
o MtDNA is more prone to contamination from extraneous sources
because of:
1. High copy number in conjunction with
2. PCR selectivity
o Main concern in the in R. v. Murrin voir dire trial
o In order to understand how a lab is structured to control for
contamination the whole process requires review
Controls for mtDNA Analysis
o Bacteria or fungiprimer design (a primer or oligonucleotide is
species specific if large enough!)
o All personnel in the field and lab should have their DNA profiles on
file to rule them out as a potential source of contamination
o Clean Lab where special controls of evidentiary samples are
carried out including separate areas for evidentiary and exemplar
Contamination Controls: Lab
o Lab design separate areas for processing exemplar and
comparison samples
o Clean room with positive air flow
o Stringent procedural controls to prevent modern contamination
o Negative controls in electrophoresis runs
o Careful laboratory practices: Experiments carried out in a clean
lab facility
o Protective clothing
o Sterilization of equipment and reagents
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