Role of helicase and DNA polymerase explains how DNA is copied, checked, amplified or analysed through specific strand relationships, enzymes and molecular techniques.
Coverage 2015–2020 · Updated 16 Jul 2026
Helicase separates the two DNA strands, while DNA polymerase builds complementary DNA strands from the exposed templates.
Helicase unwinds the double helix and breaks hydrogen bonds between complementary bases. DNA polymerase selects complementary DNA nucleotides and joins them into a growing strand.
Helicase: unwind and break inter-strand hydrogen bonds. DNA polymerase: use each original strand as a template and join complementary nucleotides.
At a replication fork, helicase exposes template bases; polymerase then places A opposite T and C opposite G while extending the new DNA.
Helicase does not synthesize DNA, and polymerase does not separate the original strands. Detailed 5′/3′ directionality belongs to the later HL objective.
This objective is assessed through multiple choice, structured response, commonly using Explain / Outline / Identify.
Explain / Outline / Identify
Build the answer around this relationship: Role of helicase and DNA polymerase depends on matching each strand, enzyme or laboratory step to its exact function.
Saying both parental strands stay together instead of one parental strand entering each daughter molecule.
Representative question
What is a function of the enzyme helicase?
It coils DNA up into a double helical shape.
It links DNA nucleotides in a new DNA strand.
It breaks hydrogen bonds between the DNA strands.
It forms temporary hydrogen bonds to produce messenger RNA.
DNA replication produces exact DNA copies before cell division and maintains genetic continuity for reproduction, growth, and tissue replacement. Semi-conservative replication gives each new DNA molecule one original strand and one new strand; complementary base pairing and Meselson-Stahl isotope evidence support the model. Helicase unwinds DNA and breaks hydrogen bonds; DNA polymerase joins complementary nucleotides to build new strands. PCR amplifies selected DNA using primers, temperature cycles, and Taq polymerase; gel electrophoresis separates DNA fragments by size and charge. PCR and gel electrophoresis support DNA profiling for forensic identification and paternity testing.
