DP Biology (first assessment 2025)

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Question 21M.1A.HL.TZ2.28

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Date May 2021 Marks available [Maximum mark: 1] Reference code 21M.1A.HL.TZ2.28
Level HL Paper 1A Time zone TZ2
Command term Question number 28 Adapted from N/A
28.
[Maximum mark: 1]
21M.1A.HL.TZ2.28

The mRNA codon UAC codes for the amino acid tyrosine. Which tRNA carries tyrosine?

[1]

Markscheme

B

Examiners report

The G2 forms raised two concerns with this question.

Firstly, the use of the term codon to describe a DNA sequence of 3 bases when this term is normally used for sequences of bases on mRNA. It is normal to use the term triplet referring to bases on a strand of DNA though codon is an accepted but infrequently used alternative.

Secondly, the question does not make it clear if it is referring to the sense or antisense strand, both of which would give different responses.

Both answers C and D were accepted as correct, and the question will be changed before the paper is published.

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