- 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
Null Alleles
Home > STR Data Analysis & Interpretation > Data Troubleshooting > Mutations > Null Alleles
A null allele is an allele that is present in a sample, yet is not amplified. A primer binding site mutation can inhibit amplification for that allele and result in a null allele. If an individual is heterozygous and has a primer binding site mutation for one of the alleles, the individual would type as a homozygote.
| Note: |
The manufacturers of various STR typing kits use different primer sets. If a DNA sample has a mutation in a primer binding region specific to kit A, but no mutation in the primer binding region specific to kit B, a rare discordance in allele calls can occur when comparing typing results produced by these two manufacturers' kits.07 |
When comparing DNA typing results from different kits, null alleles (due to primer binding site mutations) can result in discrepant DNA types at a particular locus. It is important to understand that although null alleles are rare, they must be considered when interpreting potential matches.
