| Date | May 2021 | Marks available | 1 | Reference code | 21M.1.SL.TZ2.10 |
| Level | Standard level | Paper | Paper 1 | Time zone | Time zone 2 |
| Command term | Question number | 10 | Adapted from | N/A |
Question
Bacteria cultured in a medium containing only 15N were transferred to a medium containing only 14N and allowed to complete one round of replication. The DNA in bacteria produced as a result of replication on the 14N medium was extracted and subjected to caesium chloride centrifugation which separates DNA molecules according to their density.
Which centrifuge tube shows the arrangement of bands observed after one round of replication?
A. Tube 3
B. Tube 4
C. Tube 5
D. Tube 6
Markscheme
D
Examiners report
The candidates found this question difficult, but it did discriminate well. This was a common question with HL and the HL students performed better than SL on the question as would be expected.
Syllabus sections
- 17M.1.SL.TZ2.9: Which are necessary to make DNA replication semi-conservative? I. Separation of the strands...
-
16N.2.SL.TZ0.7b:
Producers extract phosphates and nitrates from soil. Outline how these ions are used in the synthesis of organic molecules.
- 21N.1.SL.TZ0.11: The data shows part of the genetic code for mRNA. Which anticodon could be found on a tRNA...
- 19N.2.SL.TZ0.2d.i: Annotate the diagram to show a peptide bond between two amino acids.
- 17M.2.HL.TZ2.1f.i: State the name of the molecule which is produced by transcription.
- 18N.1.SL.TZ0.8: Where are amino acids joined together to make polypeptides? A. Nucleus B. Nucleolus C. ...
- 22M.1.SL.TZ1.7: Which reaction occurs when a dipeptide is formed from amino acids? A. Hydrolysis B....
- 22M.1.SL.TZ1.10: What is the minimum number of nucleotides needed to code for a polypeptide composed of 210...
- 18N.1.SL.TZ0.9: The table shows some codons for five amino acids. Which of these DNA strands will code for...
- 17N.1.SL.TZ0.11: Which sequence of bases and amino acids could be produced by transcription and translationof...
- 22M.1.HL.TZ2.11: Bacteria can be genetically modified to produce human insulin. The diagram shows how the...
- 17M.1.SL.TZ1.8: Meselson and Stahl conducted experiments using the isotopes 14N and 15N which showed that DNA...
-
21M.2.HL.TZ2.7b:
Outline the role of three enzymes used in the replication of DNA.
- 18M.1.SL.TZ1.12: What do DNA replication, transcription and translation have in common? A. Take place in cell...
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18M.1.HL.TZ2.8:
Meselson and Stahl investigated DNA replication by first feeding bacteria with bases containing 15N (heavy), and then with bases containing 14N (light). The results are shown in the photographs.
[Source: © International Baccalaureate Organization 2018]
From this information, what would be the composition of the DNA in generation 3?
A. There will be a single 14N band.
B. There will be a single 15N band and a single 14N band.
C. There will be a darker 14N band and a lighter hybrid band.
D. There will be a single 15N band, a single hybrid band and a single 14N band.
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17M.1.HL.TZ1.9:
A strand of mRNA consists of the following nucleotides:
AUUCUGGCUA
Which of the following represents the non-transcribed (sense) strand of the DNA?
A. TAAGACCGAT
B. ATTCTGGCTA
C. UAAGACCAU
D. AUUCUGGCUA
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
- 21N.1.SL.TZ0.10: What is the correct arrangement for the components of one strand in a DNA molecule?
- 18M.1.HL.TZ1.9: What do DNA replication, transcription and translation have in common? A. Take place in cell...
- 17M.1.SL.TZ1.11: A short sequence of nucleotides reads GGACAGAGCGCAGACGA. In which type of molecule could this...
- 19N.2.SL.TZ0.2c: Suggest a hypothesis that accounts for the slightly different meaning of some codons in a...
-
19N.2.SL.TZ0.2e:
Outline the function of Rubisco and of spider silk in relation to their three-dimensional conformation.
- 17M.1.SL.TZ1.12: The table shows the genetic code. Which mRNA could code for the sequence...
-
17M.2.SL.TZ1.5b:
Describe the polymerase chain reaction (PCR), including the role of Taq DNA polymerase.
- 19N.2.SL.TZ0.2b.ii: Determine the DNA base sequence transcribed to form this sequence of mRNA.
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
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22M.1.SL.TZ1.6:
What are linked by hydrogen bonds?
A. Hydrogen and oxygen within a water molecule
B. Phosphate and sugar within a DNA molecule
C. Base and sugar between DNA nucleotides
D. Hydrogen and oxygen in different water molecules
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22M.2.HL.TZ2.7b:
Describe the function of three named enzymes involved in DNA replication.
- 19N.1.SL.TZ0.11: For what did Meselson and Stahl’s work provide evidence? A. The abiotic origin of organic...
- 19N.2.SL.TZ0.2d.ii: State the type of reaction that removes water while linking amino acids together to form...
- 19M.1.SL.TZ2.9: The base sequences of a short section of DNA are shown, together with mRNA that has been...
- 16N.1.SL.TZ0.11: What enables bacteria to produce human growth hormone? A. DNA replication is...
-
20N.1.SL.TZ0.10:
What is the reason for Taq DNA polymerase being used in the polymerase chain reaction (PCR)?
A. It does not denature at high temperatures.
B. It produces Okazaki fragments more rapidly.
C. It allows translation to proceed rapidly.
D. It works efficiently with helicase in PCR.
- 17M.2.SL.TZ2.5b: Outline the role of ribosomes in translation.
- 19N.2.SL.TZ0.2b.i: Determine the sequence of amino acids that could be translated from the sequence of mRNA.
- 19N.2.SL.TZ0.2a: Outline the function of codons.
-
20N.1.SL.TZ0.9:
The diagram represents transcription and translation.
[Source: © International Baccalaureate Organization 2020.]
What structures do the letters X and Y represent?
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19N.1.HL.TZ0.7:
The diagram shows mRNA codons.
[Source: elementix / Alamy Stock Photo]
The mRNA sequence UGGAACGUA codes for what amino acid sequence?
A. Glycine-Glutamine-Methionine
B. Methionine-Glutamine-Glycine
C. Threonine-Valine-Histidine
D. Tryptophan-Asparagine-Valine
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18M.2.HL.TZ1.4b:
DNA codes for the amino acid sequence of polypeptides. List two other functions of DNA.
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
-
21M.2.HL.TZ1.8b:
Outline the role of DNA polymerase III in DNA replication.
-
21M.2.HL.TZ2.7c:
Insulin is produced in β cells of the pancreas and not in other cells of the human body. Explain how differentiation of cells and regulation of gene expression allow proteins such as insulin to be produced in only certain types of body cell.
- 18M.2.SL.TZ2.2c.ii: Outline the role of the enzyme DNA polymerase in replication.
- 18M.1.SL.TZ2.12: Some yeast genes can be replaced by human genes that then continue to produce the same human...
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
- 19M.1.SL.TZ1.10: The gene that codes for a particular polypeptide includes the base sequence...
-
22M.2.SL.TZ2.6a:
Outline how a protein is made in a cell by the process of translation.
- 19M.2.HL.TZ1.7a: Outline the roles of helicase and ligase in DNA replication.
- 19M.2.SL.TZ1.7a: Outline the stages in the production of mRNA by transcription.
- 17M.2.SL.TZ1.5a: Outline how translation depends on complementary base pairing.
-
17N.2.HL.TZ0.07b:
Nitrogen is part of many important substances in living organisms.
Distinguish between transcription and translation.
- 21M.1.SL.TZ2.9: Which feature is common to both mRNA and DNA? A. Covalent bonds between adjacent...
-
18M.2.SL.TZ2.2c.i:
Outline the role of the enzyme helicase in replication.
