IB Biology SL D1.1 Dna Replication Questions

Practise IB Biology SL D1.1 by explaining replication steps and applying DNA principles to PCR, electrophoresis and profiling.

Exam points

explain DNA replication before cell division using template strands, free nucleotides and complementary base pairing
identify one original and one newly synthesized strand and interpret Meselson–Stahl isotope-density evidence
distinguish helicase unwinding and hydrogen-bond breaking from DNA polymerase nucleotide addition
explain PCR amplification through denaturation, primer annealing and Taq-polymerase extension
interpret gel electrophoresis separation and DNA-profile band patterns by fragment size
apply PCR, fragment separation and band patterns to paternity or forensic conclusions

Covered syllabus points

D1.1.1—DNA replication D1.1.2—Semi-conservative replication D1.1.3—Role of helicase and DNA polymerase D1.1.4—PCR and gel electrophoresis D1.1.5—Applications

[Maximum number: 1]

What is required to replicate DNA?

Temperature of $37^{\circ} \mathrm{C}$

Free nucleotides carrying A, C, G and T bases

Plasmids

Endonuclease

[Maximum number: 1]

Meselson and Stahl grew bacteria in a medium with ${ }^{15} \mathrm{~N}$ (heavy nitrogen) so that all bacteria in the parental culture contain heavy DNA. They then transferred some of the bacteria to a medium with ${ }^{14} \mathrm{~N}$ (light nitrogen).

Samples were taken at 0,20 and 40 minutes and centrifuged with the results as shown.

State the conclusion Meselson and Stahl drew from their experiment.

[Maximum number: 1]

Outline the role of the following enzymes in replication.

Outline the role of helicase in DNA replication.

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Covered syllabus points

Question 1

Question 2

Question 3