Allele Drop-in
Definition
Appearance of a low-level allele in a PCR product from stochastic amplification of a contaminant molecule. More common in low-template reactions where even single molecules can produce visible peaks.
- Mechanism
- Stochastic amplification of a contaminant molecule
- Context
- Low-template PCR reactions
- Effect
- Appearance of a spurious low-level allele
- Related phenomenon
- Allele drop-out
Common questions
Why is drop-in more of a risk in low-template samples specifically?+
With very few starting template molecules, a single contaminant DNA molecule present in the reaction can be amplified to a visible peak alongside the genuine sample, whereas in a normal-template reaction that same contaminant would be diluted into insignificance.
How do analysts distinguish a drop-in peak from a true minor contributor in a mixture?+
Drop-in peaks are typically low in height relative to the main profile and inconsistent between replicate amplifications of the same extract, so running replicates and comparing peak heights against validated stochastic thresholds helps flag likely drop-in rather than a genuine minor contributor.
Related terms
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