DP Biology (first assessment 2025)

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Question 20N.2.SL.TZ0.4a

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Date November 2020 Marks available [Maximum mark: 3] Reference code 20N.2.SL.TZ0.4a
Level SL Paper 2 Time zone TZ0
Command term Sketch Question number a Adapted from N/A
a.
[Maximum mark: 3]
20N.2.SL.TZ0.4a
(a)

Sketch the complementary strand to complete the section of a DNA diagram.

[3]

Markscheme

a. correct base sequence: T, G, A;

b. strand drawn anti-parallel;

c. correct shapes used;

Award [2 max] if bonds are not from the correct carbon or if the nucleotides are not joined.

Examiners report

In part (a) most could gain marks for the correct shapes and sequence but did not gain the third mark as it was not shown as antiparallel. Some lost marks as a 2MAX was awarded if the bonds were not from the correct carbons. In part (b) the definition of mutation was quite well known, and most gained some marks in the explanation. Weaker students just wrote about evolution without relating it to mutations as asked. They also tended to give unnecessary examples, involving finches and moths etc.

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