Haematin
Definition
Degradation product of haemoglobin that inhibits Taq polymerase by chelating Mg2+ ions and binding to the polymerase active site; most common inhibitor in blood-related forensic extracts.
- Origin
- Degradation product of haemoglobin
- Mechanism
- Chelates Mg2+ ions, binds polymerase active site
- Effect
- Inhibits Taq polymerase
- Relevance
- Most common inhibitor in blood-related forensic extracts
Common questions
Why does haematin specifically interfere with PCR amplification?+
Taq polymerase requires free magnesium ions as a cofactor to function, and haematin binds Mg2+ as well as directly interacting with the enzyme's active site, so its presence in an extract can suppress or completely block amplification even when intact template DNA is present.
How do forensic laboratories work around haematin inhibition in bloodstain samples?+
Common approaches include additional DNA purification steps to remove haematin before amplification, diluting the extract to reduce inhibitor concentration, or using PCR reagent formulations and polymerases specifically designed to tolerate blood-derived inhibitors.
Related terms
- Allelic Drop-Out
- Failure of one allele of a heterozygous locus to amplify detectably, a stochastic effect of low-template amplification where sampling of limited template...
- ESSplex SE QS
- Qiagen kit covering the European Standard Set of 17 loci plus DYS391 and Amelogenin; optimised for EU Prüm database upload.
- GlobalFiler
- Applied Biosystems 25-plex STR kit covering 24 STR loci plus Amelogenin, compatible with both CODIS 20 and ESS17 requirements.
- Humic Acid
- Organic polymer from soil degradation that inhibits PCR by intercalating into double-stranded DNA and disrupting primer annealing.
- Identifiler Plus
- Applied Biosystems 16-plex STR kit covering the original 13 CODIS loci plus D2S1338, D19S433, and Amelogenin. Widely used through the 2010s; insufficient...
- Investigator 24Plex QS
- Qiagen 26-plex STR kit with Quality Sensor (IPC) and covering 24 STR loci plus DYS391 and Amelogenin. GO! variant uses increased cycles...
- IPC (Internal PCR Control)
- A non-forensic DNA sequence spiked into the PCR reaction at fixed concentration; a shift in IPC Ct value relative to the expected...
- Low-Copy-Number (LCN) PCR
- PCR protocol using increased cycle numbers (typically 34 cycles) developed at the UK FSS to generate profiles from template inputs below ~100...
- PowerPlex Fusion 6C
- Promega 23-plex STR kit covering all 20 CODIS core loci, all 17 ESS loci, DYS391, and Amelogenin across 6 dye channels.
- Probabilistic Genotyping
- Software-based interpretation of complex DNA electropherograms using continuous statistical models (e.g. STRmix, TrueAllele, ArmedXpert). Generates a likelihood ratio for complex mixtures previously...