Venous blood is collected from a suspect for reference DNA profiling. Which anticoagulant containing tube should be used, and why?
- A EDTA, because heparin inhibits the Taq polymerase used in PCR ✓
- B Sodium heparin, because it best preserves leukocyte morphology
- C Sodium citrate, because it yields the highest DNA concentration per millilitre
- D Plain clotted tube, because serum contains abundant nuclear DNA
Correct answer: A. EDTA, because heparin inhibits the Taq polymerase used in PCR
Explanation
EDTA chelates divalent cations and preserves genomic DNA from nucleases, whereas residual heparin carried through extraction potently inhibits Taq polymerase and causes amplification failure. Citrate provides weaker anticoagulation and dilutes the specimen, and serum contains little cellular DNA since nuclear material resides in leukocytes, which are retained in the clot. EDTA blood is therefore the standard reference sample for DNA work.
Reference: Butler, Forensic DNA Typing, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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