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Date May 2022 Marks available 1 Reference code 22M.1.HL.TZ2.26
Level Higher level Paper Paper 1 Time zone Time zone 2
Command term Question number 26 Adapted from N/A

Question

The diagram shows the structure of a nucleosome.

[Source: Zephyris. Nucleosome 1KX5 colour coded. Available at https://en.wikipedia.org/wiki/Nucleosome#/media/File:Nucleosome_1KX5_colour_coded.png 
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license (https://creativecommons.org/licenses/by-sa/3.0/deed.en).]

 

What is the structure labelled T?

A. 5' end of RNA

B. 5' end of uncoiled DNA

C. N-terminal tail of one DNA strand

D. N-terminal tail of one histone

Markscheme

D

Examiners report

This question received some criticism in the comments on the G2 forms. It was suggested that this question was too difficult for IB level students, the diagram was not clear and the term ‘N terminal tail’ was out of the scope of the IB guide. The question related to 7.1 in the biology guide “Utilization of molecular visualization software to analyse the association between protein and DNA within a nucleosome”. Despite criticism, the question did discriminate well, possibly because the more able students were able to eliminate the incorrect responses by looking at the diagram leaving response D as the correct response. It is understood that questions on multiple choice tests would not normally be expected to be answered by this means.

Syllabus sections

Additional higher level » Topic 7: Nucleic acids » 7.1 DNA structure and replication
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