| Date | May 2021 | Marks available | 1 | Reference code | 21M.1.HL.TZ2.28 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 2 |
| Command term | Question number | 28 | Adapted from | N/A |
Question
The mRNA codon UAC codes for the amino acid tyrosine. Which tRNA carries tyrosine?
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.
Syllabus sections
- 17M.1.HL.TZ2.11: This image is taken from a visualization of a eukaryotic ribosome. The arrows show the...
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18M.1.HL.TZ2.12:
In which image are polysomes visible? (The images do not have the same magnification)
- 17M.1.HL.TZ2.9: Scientists have heated a solution containing the protein albumin and measured its relative...
- 16N.1.HL.TZ0.26: Where does a tRNA-activating enzyme attach the appropriate amino acid to the tRNA molecule?
- 18M.2.HL.TZ2.4a: The diagram shows alpha amylase. Explain the secondary structure of this protein molecule.
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18M.2.HL.TZ2.2c.ii:
Outline the role of tRNA activating enzymes in translation.
- 18M.2.HL.TZ2.2c.i: Outline the role of the A-site of ribosomes in translation.
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18N.2.HL.TZ0.2a.i:
Label a peptide bond in the diagram of a polypeptide.
- 17M.1.SL.TZ1.1: Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C....
- 16N.1.HL.TZ0.27: What does post-transcriptional modification of eukaryotic mRNA include? I. Introns are...
- 18M.1.HL.TZ1.28: What are polysomes? A. Strings of amino acids B. Packages of eight histones with DNA C....
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22M.1.HL.TZ1.28:
This DNA sequence was used to synthesize a polypeptide.
DNA (sense strand): 3′ T A C T G A 5′
DNA (template strand): 5′ A T G A C T 3′
Which are the bases of the tRNA (anticodons)?
A. T A C T G A
B. U A C U G A
C. A U G A C U
D. A T G A C T
- 17N.1.HL.TZ0.28: Which cell component synthesizes actin and myosin? A. Free ribosomes B. Rough endoplasmic...
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22M.1.HL.TZ2.28:
The diagram shows the structure of E. coli ribonuclease HI, a bacterial protein consisting of one polypeptide chain.
[Source: RCSB PDB. 1JL1 D10A E. coli ribonuclease HI. PDB DOI: 10.2210/pdb1JL1/pdb Mol* (Goedken, E.R., Marqusee, S. Native-state energetics of a thermostabilized variant of ribonuclease HI. (2001) J Mol Biol 314:
863–871 DOI:10.1006/jmbi.2001.5184) [image online] Available at: https://www.rcsb.org/structure/1jl1
[Accessed 25 November 2019]. This file is licensed under the Creative Commons CC0 1.0 Universal (https://creativecommons.org/publicdomain/zero/1.0/).]Which level(s) of protein structure is/are shown?
A. Alpha helix only
B. Quaternary only
C. Primary and secondary
D. Secondary and tertiary
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20N.1.HL.TZ0.28:
The diagram shows the three-dimensional structure of tRNA.
[Source: Structure reproduced with the kind permission of N.R. Voss.]
What can attach to the region marked X?
A. mRNA
B. An amino acid
C. An anticodon
D. The P site of the ribosome
- 17M.1.HL.TZ1.28: Which types of interactions are found in a part of a protein with secondary but not tertiary...
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21N.2.HL.TZ0.4b:
Describe the secondary structure of proteins.
- 18M.2.HL.TZ1.4c: Distinguish between the purpose of free and bound ribosomes.
- 18N.2.HL.TZ0.2a.ii: Outline the primary structure of proteins.
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19M.1.HL.TZ1.28:
The image shows a polysome in a bacterial cell.
[Source: © International Baccalaureate Organization 2019]
How many genes have been transcribed?
A. 1
B. 2
C. 3
D. 4
- 19N.1.HL.TZ0.28: How do R group interactions contribute to protein structure? I. Determining the sequence of...
- 17M.2.HL.TZ2.6b: Outline the roles of the different binding sites for tRNA on ribosomes during translation.
- 16N.1.HL.TZ0.28: Variations in the types of antibodies are produced by mRNA splicing. What is an advantage of...
- 19N.2.HL.TZ0.6c: Explain how a polypeptide chain is synthesized in a eukaryotic cell.
-
17N.2.HL.TZ0.07b:
Nitrogen is part of many important substances in living organisms.
Distinguish between transcription and translation.
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20N.2.HL.TZ0.6c:
Explain how polypeptides are produced by the process of translation.
-
19N.1.HL.TZ0.27:
In the diagram of a ribosome, which letter indicates the P site?
[Source: iStock.com/ttsz]
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21N.1.HL.TZ1.28:
What is the primary function of the free ribosomes shown in the electron micrograph?
[Source: J Gordon Betts, et al. Anatomy and Physiology. Houston Texas: OpenStax, 2013. https://openstax.org/books/
anatomy-and-physiology/pages/3-2-the-cytoplasm-and-cellular-organelles. Image file available at https://commons.
wikimedia.org/wiki/File:0313_Endoplasmic_Reticulum.jpg#/media/File:0313_Endoplasmic_Reticulum_b_labeled.
png. This file is licensed under the Creative Commons Attribution 3.0 Unported license. https://creativecommons.org/
licenses/by/3.0/deed.en.]A. Synthesize proteins to be used within the cell
B. Synthesize proteins for use in lysosomes
C. Carry amino acids to mRNA for protein synthesis
D. Synthesize proteins for secretion
