- Course Introduction
- 01: Evidence & DNA
- 02: Forensic Biology
- 03: DNA Extraction & Quantitation
- 04: DNA Amplification
- 05: Amplified DNA Product Separation
- 06: STR Data Analysis & Interpretation
- Data Troubleshooting
- Data Interpretation & Allele Calls
President's DNA Initiative
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Advancing Justice Through DNA Technology
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Advancing Justice Through DNA Technology
DNA Analyst Training
Stochastic Effects
Home > STR Data Analysis & Interpretation > Data Troubleshooting > Stochastic Effects
Stochastically-induced heterozygote imbalance may be observed in STR analysis due to the effective low copy number of DNA templates in degraded DNA.
The amplification process can produce many copies from a relatively low quantity of DNA. If too small a quantity of DNA is introduced at the beginning of amplification, it is possible that heterozygous alleles may amplify differentially. The first few cycles of the amplification process are extremely important; if imbalanced amplification occurs, it will result in stochastic effects.
An analyst can assess the data by calculating the heterozygosity of alleles. If the heterozygosity is less than 70%, this could indicate a mixture and/or stochastic amplification.
Click here to view an animation that shows an example of the stochastic effect.
