Allele Drop-Out
Definition
Failure of one allele at a heterozygous locus to amplify in a low-template PCR reaction, producing an apparent homozygote. Increases dramatically below approximately 100 pg template.
- Mechanism
- Failure of one allele to amplify at a heterozygous locus
- Result
- Apparent homozygote
- Context
- Low-template PCR
- Threshold
- Increases sharply below about 100 pg template
Common questions
Why does drop-out matter for interpreting a mixed or partial DNA profile?+
A locus that appears homozygous because of drop-out can be mistakenly excluded as a match to a true contributor whose second allele simply failed to amplify, so probabilistic genotyping software must model drop-out probability rather than reading peaks at face value.
What laboratory practice helps detect when drop-out has likely occurred?+
Running replicate amplifications from the same low-template extract and comparing which alleles appear consistently across replicates helps analysts distinguish a true homozygous locus from one where drop-out removed a real second allele in a given run.
Related terms
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