DP Biology (first assessment 2025)

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Question 22M.2.SL.TZ2.a.ii

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Date May 2022 Marks available [Maximum mark: 2] Reference code 22M.2.SL.TZ2.a.ii
Level SL Paper 2 Time zone TZ2
Command term Explain Question number a.ii Adapted from N/A
a.ii.
[Maximum mark: 2]
22M.2.SL.TZ2.a.ii

Explain how the two strands of the DNA double helix are held together.

[2]

Markscheme
  1. hydrogen bonding between nucleotides / bases;
  2. complementary base pairs;
  3. adenine-thymine and cytosine-guanine form base pairs (between the two strands with H-bonding);
  4. 2 bonds between A and T, while 3 bonds between C and G;

OWTTE

Full names required for c and d though use ecf.

Syllabus sections