Hot-Start Polymerase
Definition
Any Taq formulation (antibody-mediated, chemically modified, or aptamer-blocked) that is inactive below ~60°C, preventing non-specific amplification during reaction setup.
- Activation threshold
- Inactive below approximately 60 degrees C
- Formulation types
- Antibody-mediated, chemically modified, aptamer-blocked
- Base enzyme
- Taq polymerase formulation
- Forensic benefit
- Prevents non-specific amplification during reaction setup
Common questions
Why does preventing non-specific amplification matter for forensic STR typing?+
Low-template forensic samples are especially vulnerable to primer-dimer and mispriming artefacts forming at room temperature before cycling begins, which can consume reagents and generate spurious peaks that complicate interpretation of an already sparse profile.
How do the different hot-start mechanisms differ in practice?+
Antibody-bound enzyme releases once the antibody denatures at the first high-temperature step, chemically modified enzyme requires a prolonged activation incubation to remove blocking groups, and aptamer-blocked enzyme releases more rapidly, so kit protocols specify the activation time matched to their chemistry.
Is hot-start chemistry standard in current forensic STR kits?+
Yes, essentially all modern commercial multiplex STR kits use a hot-start Taq formulation, which is why kit protocols specify an initial denaturation and activation hold before cycling starts.
Related terms
- A-Addition
- The non-templated addition of a single adenine nucleotide to the 3' end of PCR products by Taq polymerase, exploited in forensic STR...
- AmpliTaq Gold
- A chemically modified hot-start form of Taq polymerase (Applied Biosystems) that is inactive at room temperature and requires a 10-11 minute activation...
- Annealing Temperature
- The reduced temperature (50-65°C) at which primers hybridise to single-stranded template. Determined by primer Tm; set to balance specificity against yield.
- Denaturation
- The separation of double-stranded DNA into two single strands by disrupting the hydrogen bonds between base pairs. In PCR, denaturation is achieved...
- Extension
- The PCR step at ~72°C at which thermostable DNA polymerase synthesises a new complementary strand from each primer, using dNTPs in the...
- Melting Temperature (Tm)
- The temperature at which half of a primer-template duplex population is dissociated. Depends on primer length, GC content, and nearest-neighbour stacking interactions.
- Negative Amplification Control
- A no-template reaction well run alongside case samples; any amplified peak indicates reagent contamination or analyst-introduced contamination during setup.
- Uni-Directional Workflow
- The physical principle governing forensic DNA laboratory layout: personnel and materials move from pre-PCR to post-PCR zones only, preventing high-copy-number amplified products...