PCR initial denaturation is done at
Initial denaturation represents the first prolonged high-temperature step in PCR designed to ensure complete separation of complex genomic double-stranded DNA, resolve secondary structures, eliminate residual nucleases, and in hot-start protocols, activate chemically modified or antibody-blocked polymerase. Conducted at 94-95°C for 1-5 minutes, this temperature efficiently breaks hydrogen bonds between bases, converting template to single-stranded form accessible to primers. Insufficient temperatures of 50-75°C fail to fully denature high GC regions, leading to incomplete template availability and drastically reduced yield. Hence high-temperature initiation is crucial before cycling begins.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.