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Increasing amplification success of forensic DNA samples using multiple displacement amplification.
Kaye N Ballantyne1, Roland A H van Oorschot, R John Mitchell
1Biology Division, Victoria Police Forensic Services Centre, 31 Forensic Drive, Macleod, 3085, VIC, Australia, kaye.ballantyne@police.vic.gov.au.
Forensic Science, Medicine, and Pathology
|April 15, 2015
Summary
Molecular crowders improve DNA amplification from trace evidence. This technique enhances short tandem repeat genotyping success and reduces amplification bias in forensic samples.
Area of Science:
- Forensic Science
- Molecular Biology
- Genetics
Background:
- Multiple displacement amplification (MDA) is a method for amplifying DNA from small quantities.
- Standard MDA can exhibit preferential amplification and allelic dropout when amplifying limited DNA amounts (<100 pg).
- These biases can compromise the accuracy and completeness of DNA profiles, particularly in forensic casework.
Purpose of the Study:
- To evaluate the effectiveness of molecular crowders in improving MDA performance on low-concentration forensic samples.
- To assess the impact of crowded MDA on short tandem repeat (STR) genotyping success and amplification bias.
- To compare standard MDA with crowded MDA using various forensic sample types (blood, semen, saliva, hair, trace DNA).
Main Methods:
- Standard and crowded MDA protocols were applied to low-concentration DNA samples from diverse forensic sources.
- Molecular crowders, specifically polyethylene glycol 400, were incorporated into the MDA reaction.
- Amplification success, allelic dropout, and amplification bias were analyzed for both methods.
Main Results:
- Crowded MDA demonstrated an average increase of 15% in the number of alleles obtained compared to standard MDA.
- A significant reduction in amplification bias was observed with crowded MDA.
- Standard MDA showed no significant improvement in STR genotyping success on these challenging samples.
Conclusions:
- The addition of molecular crowders to MDA significantly enhances DNA profile quality from low-concentration forensic samples.
- Crowded MDA improves STR genotyping success rates and reduces allelic dropout and amplification bias.
- This optimized MDA technique offers a valuable tool for analyzing challenging casework samples in forensic investigations.
