| Date | November 2020 | Marks available | 1 | Reference code | 20N.1.SL.TZ0.8 |
| Level | Standard level | Paper | Paper 1 | Time zone | TZ0 / no time zone |
| Command term | Question number | 8 | Adapted from | N/A |
Question
The genetic code is shown.
In a coding gene, the DNA triplet in the transcribed strand is changed from AGG to TCG.
What would be the result of this change in the genome?
A. A non-functional protein
B. A different but functional protein
C. No change in the protein
D. Termination of the polypeptide
Markscheme
C
Examiners report
This was another poorly answered question with only slightly more than 25 % answering correctly - the expected success rate with guessing. However, the discrimination index was high, showing that well-prepared candidates tended to get it right and weaker candidates mostly chose one of the distractors, with B proving particularly popular. It was necessary to realise from the presence of U rather than T that the chart gave the genetic code in terms of mRNA base sequences, not DNA. The DNA base sequence of the transcribed strand given in the question therefore had to be converted to the complementary RNA base sequence that results from transcription. Then the amino acid coded for before and after the base change had to be deduced from the chart. This gave the result of serine both before and after the base change, leading to answer C – no change in the protein. If candidates thought that the mRNA triplet was the same as the DNA triplet apart from U instead of T, they would have expected the amino acid to be different, directing them to one of the three distractors.
Syllabus sections
-
22M.1.HL.TZ2.6:
The diagram shows the structure of the protein CXCL12.
[Source: Lu, J., Chatterjee, M., Schmid, H. et al. CXCL14 as an emerging immune and inflammatory modulator.
J Inflamm 13, 1 (2016). https://doi.org/10.1186/s12950-015-0109-9 Distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).]Which chemical group is found at X?
A. NH2
B. NOH
C. COH
D. COOH
- 17N.1.HL.TZ0.05: Which of the molecules contain peptide bonds or are sugar molecules?
- 16N.1.SL.TZ0.7: The diagram shows a molecular structure. Which type of molecule is shown? A. Amino acidB....
- 17M.2.SL.TZ2.5a: Draw a molecular diagram of an amino acid to show its general structure.
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21N.1.HL.TZ1.6:
The image shows the structure of the protein hemoglobin
[Source: Hemoglobin molecule, Microbiology ID: e42bd376-624b-4c0f-972f-e0c57998e765@4.4 OpenStax Microbiology
https://cnx.org/contents/5CvTdmJL@4.4 and https://commons.wikimedia.org/wiki/File:OSC_Microbio_07_04_
hemoglobin.jpg Licensed under a Creative Commons Attribution 4.0 International License,
https://creativecommons.org/licenses/by/4.0.]What level of protein structure bonds the α and β chains together?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
- 17N.1.SL.TZ0.06: Which molecule could be hydrolysed into amino acids?
- 22M.2.SL.TZ1.2a: State how many different types of amino acid there are, which can become part of a...
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18M.1.SL.TZ1.9:
Which protein has the highest tensile strength (ability to resist breaking when stretched)?
A. Cellulose
B. Actin
C. Spider silk
D. Albumin
- 18M.1.SL.TZ2.10: Which description matches the protein?
- 17M.3.SL.TZ2.2c: State two conditions that should be kept constant in both experiments.
- 17M.3.SL.TZ2.2b: Suggest two changes occurring in the reaction vessel that could be used to indicate...
-
22M.2.SL.TZ1.2c:
Explain how denaturation affects the activity of an enzyme.
- 22M.1.SL.TZ2.9: People who suffer from night blindness cannot see well at night because their retinal cells...
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19M.1.SL.TZ1.9:
The graph shows the results of an investigation into the activity of turnip peroxidase. The accumulation of the product of the reaction catalysed by the enzyme is shown at different pH values.
[Source: © International Baccalaureate Organization 2019]
Based on the data in the graph, what is most probably the optimum pH for turnip peroxidase?
A. Between 3 and 5
B. Between 10 and 11
C. Between 7 and 8
D. Between 9 and 10
- 19N.1.HL.TZ0.6: What is a proteome? A. The genes that code for all the proteins in the ribosome B. The...
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
- 17M.3.SL.TZ2.2a: Determine the optimum pH and temperature of keratinase.
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
- 17M.1.SL.TZ1.15: How does the proteome of a species contain a larger number of proteins than genes that code...
- 21N.2.SL.TZ0.2b: Outline the specific functions of three named proteins.
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
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21M.2.SL.TZ2.3c:
State the genus of the plant where this Rubisco is found.
- 21M.2.SL.TZ1.6a: Outline the structure of proteins.
-
21M.2.SL.TZ2.3d:
Outline one factor that could affect the activity of Rubisco.
- 17M.2.HL.TZ1.6a: Describe the functioning of immunoglobulins.
- 21M.2.HL.TZ2.6c: The enzyme Rubisco is used in carbon fixation during photosynthesis. Identify four other...
-
21M.2.SL.TZ1.6c:
Outline the range of functions of proteins in cells.
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21M.2.SL.TZ2.3a:
State one function of Rubisco.
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
- 22M.2.SL.TZ1.2b: Outline one cause of denaturation in proteins.
- 19M.1.SL.TZ1.8: What is found in insulin molecules? A. Phosphates B. Nucleotides C. Peptide bonds D....
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19M.1.HL.TZ2.9:
The graph shows the activity of an enzyme at different temperatures.
[Source: © International Baccalaureate Organization 2019]
What does the dashed line in the graph represent?
A. Increasing temperature increases substrate concentration.
B. Increasing temperature affects the active site.
C. Increasing temperature increases the rate of reaction.
D. Increasing temperature decreases the movement of particles.
- 17M.1.SL.TZ1.9: The most abundant structural protein in the human body is found in ligaments and skin. What...
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19M.1.SL.TZ2.8:
Which statement correctly describes genome and proteome?
A. Only the genome but not the proteome can be analysed using gel electrophoresis.
B. The genome and the proteome are the same in all tissues in an organism.
C. In cells of different tissues, the genome is the same while the proteome varies.
D. Only mutations in the proteome but not in the genome cause any variability.
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18M.2.HL.TZ1.6c:
Hydrogen bonds can exist both within and between molecules in living organisms and have an impact on their structure and function. Explain the importance of hydrogen bonding for living organisms.
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21N.2.HL.TZ0.8a:
Outline the process of protein denaturation.
- 19M.1.HL.TZ2.16: Which protein is identified with its function?
