| Date | November 2020 | Marks available | 1 | Reference code | 20N.1.SL.TZ0.5 |
| Level | Standard level | Paper | Paper 1 | Time zone | TZ0 / no time zone |
| Command term | Question number | 5 | Adapted from | N/A |
Question
How many chromosomes are there in a cell during anaphase of mitosis, if the diploid number of the cell is 20?
A. 10
B. 20
C. 40
D. 80
Markscheme
C
Examiners report
Some candidates were caught out by this question, either because their understanding of mitosis had weaknesses or because they did not think carefully enough. In anaphase, the two sister chromatids that have made up each chromosome in prophase and metaphase have separated. Guidance in sub-topic 1.6 of the program indicates that they should be referred to as chromosomes as soon as separation has occurred, rather than as chromatids. In anaphase there are therefore double the diploid number of chromosomes in a cell. Cytokinesis will subsequently halve the number, so the daughter cells are diploid.
Syllabus sections
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22M.2.HL.TZ2.2a.i:
Identify, with a reason, the stage shown at X.
- 18M.2.HL.TZ1.5a.i: Identify the structure labelled X.
- 18N.1.SL.TZ0.6: How does mitosis produce two genetically identical nuclei? A. By separation of homologous...
- 17N.1.SL.TZ0.13: What occurs during meiosis but not mitosis? A. Spindles are formed from microtubules. B....
- 17M.2.HL.TZ2.8a: Cells go through a repeating cycle of events in growth regions such as plant root tips and...
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22M.2.HL.TZ2.2a.ii:
Calculate the length of the entire cell labelled Y, showing your working.
- 18N.3.SL.TZ0.3a: Deduce, with a reason, which stage of mitosis is shown.
- 19N.1.SL.TZ0.5: Students examined micrographs and counted cells in the different stages of mitosis as well as...
- 17M.1.HL.TZ1.4: The diagram shows the concentration of four cyclins during the cell cycle. Which curve...
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21N.1.SL.TZ0.5:
The graph shows the mitotic index in the roots of lentil plants at different distances from the end of the root.
[Source: Physiologia Plantarum, Volume 105, Issue 1, January 1999, Pages 171–178, Effect of microgravity on the cell cycle
in the lentil root F. Yu, D. Driss-Ecole, J. Rembur, V. Legué, G. Perbal Wiley Online Library: https://onlinelibrary.wiley.
com/doi/abs/10.1034/j.1399-3054.1999.105125.x]What can be deduced from the graph?
A. As the distance from the end of the root increases, more cells are undergoing mitosis.
B. At 0.5 mm from the end of the root, most of the cells are in prophase.
C. There were fewer cells observed at 1.5 mm than at 0.5 mm.
D. As the distance from the end of the root increases, the percentage of cells in interphase increases.
- 19M.2.HL.TZ2.2a.ii: Outline what is indicated by the mitotic index of tissue taken from a tumour.
- 19M.1.SL.TZ2.4: Which processes are involved in the development of cancer? I. Mutations occur in...
- 17M.1.SL.TZ1.5: When during the cell cycle does DNA replication take place?
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
- 17M.1.SL.TZ2.5: The graph shows the survival probabilities for current smokers and for those who never smoked...
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18M.1.SL.TZ1.5:
The concentrations of cyclins rise and fall in cells at certain times.
[Source: https://en.wikipedia.org/wiki/Cyclin#/media/File:Cyclin_Expression.svg]
What times are these?
A. Day and night
B. Seasons of the year
C. Stages of mitosis and interphase
D. Developmental stages in the life cycle
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19N.1.SL.TZ0.4:
In the micrograph, which letter points to a cell in anaphase?
[Source: Berkshire Community College Bioscience Image Library,
https://commons.wikimedia.org/wiki/File:Mitotic_Stages_in_Apical_Meristem_of_Allium_Root_Tip_(36762516673).jpg,
licensed under Creative Commons CC0 1.0 Universal Public Domain Dedication] -
18M.1.SL.TZ2.5:
The image shows cells in the different stages of mitosis. Which cell is in telophase?
[Source: © The Trustees of Indiana University]
- 18N.3.SL.TZ0.3b: The cells visible in the onion root tip were classified and counted. Calculate the mitotic...
- 22M.1.SL.TZ2.5: Cisplatin is an anti-cancer drug that prevents tumour cells from dividing by mitosis as it...
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
- 21M.1.HL.TZ2.4: When does DNA replication occur? A. S phase of interphase B. Early prophase C. G phase of...
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22M.2.HL.TZ2.2a.iii:
State the role of cyclins in the cell cycle.
-
22M.1.SL.TZ1.5:
In the chimpanzee (Pan troglodytes), the haploid number of chromosomes is 24. How many sister chromatids are present in the G2 phase of a somatic cell, such as a cell in the bone marrow of the chimpanzee?
A. 12
B. 24
C. 48
D. 96
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17N.1.SL.TZ0.14:
Which diagram(s) represent(s) processes used in asexual reproduction?
A. I only
B. I and II only
C. II only
D. I, II and III
- 18M.2.HL.TZ1.5a.ii: State the stage of mitosis of this cell.
- 19M.1.SL.TZ1.5: The table shows the number of cells in various stages of the cell cycle in four samples of...
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16N.1.SL.TZ0.5:
Which mitotic phase is labelled X in the micrograph of an onion (Allium cepa) root tip?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase -
16N.2.HL.TZ0.2b:
Explain how the cell cycle is controlled.
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21M.2.HL.TZ1.1f:
Some anticancer drugs inhibit mitosis by blocking the formation of the spindle. Suggest one other way in which vinblastine could block mitosis.
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21M.2.SL.TZ2.2d:
The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy. Outline how the mitotic index is calculated.
- 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.HL.TZ1.1e:
By referring to both graphs, evaluate the hypothesis that vinblastine targets cells in mitosis and prevents them from completing the process.
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21M.2.SL.TZ2.2b.ii:
Using the letter M, label the stage on the diagram where sister chromatids migrate to opposite poles.
-
20N.2.HL.TZ0.2b:
Describe what happens to the membranes of an animal cell during mitosis.
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21M.2.HL.TZ1.1g:
Discuss one advantage and one disadvantage of using plant tissue to investigate drugs intended to treat cancer in humans.
Advantage:
Disadvantage:
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21M.2.SL.TZ2.2c:
Distinguish between the outcomes of a cell dividing either by mitosis or meiosis.
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
-
16N.2.SL.TZ0.2b:
(i) State the process that divides one nucleus into two genetically identical nuclei.
(ii) Explain how the cell cycle is controlled.
-
22M.1.HL.TZ1.4:
In which stage of the cell cycle are chromosomes duplicated?
[Source: M1llx, 2019. Cell cycle simple pl. [online] Available at: https://commons.wikimedia.org/wiki/File:Cell_cycle_simple_pl.png This file is licensed
under the Creative Commons Attribution-Share Alike 4.0 International license.
https://creativecommons.org/licenses/by-sa/4.0/deed.en [Accessed 1 August 2019].]A. G1 phase
B. G2 phase
C. S phase
D. Mitosis
- 18N.1.SL.TZ0.13: The diagram represents the nucleus of a cell 2 n = 8 in late prophase of mitosis. Which...
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19M.1.SL.TZ2.3:
The image shows a micrograph of a cell.
[Source: © 2014, https://commons.wikimedia.org/wiki/File:Mitosis_(261_13)_Pressed;_root_meristem_of_onion_(cells_
in_prophase,_metaphase,_anaphase,_telophase).jpg by Doc. RNDr. Josef Reischig, CSc.]What explains the appearance of the cell in the micrograph?
A. The cell is dying.
B. The DNA is replicating.
C. The cell is in metaphase.
D. The cell is in telophase.
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19M.1.HL.TZ2.17:
The diagram shows a stage in cell division.
[Source: © International Baccalaureate Organization 2019]
What is the stage shown?
A. Anaphase I of mitosis
B. Anaphase II of mitosis
C. Anaphase I of meiosis
D. Anaphase II of meiosis
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19M.2.SL.TZ2.2a:
Identify the stage of mitosis labelled X in the image, giving a reason.
[Source: Copyright 2002, The Trustees of Indiana University]
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19M.2.HL.TZ2.2a.i:
Identify the stage of mitosis labelled X in the image, giving a reason.
[Source: Copyright 2002, The Trustees of Indiana University]
- 21M.2.SL.TZ1.1e: Deduce the change in mitotic index after 72 hours compared to the control.
- 20N.1.HL.TZ0.4: What would show that a person has developed metastatic cancer? A. Alveolus cells forming a...
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21M.2.SL.TZ2.2a:
State processes occurring during interphase.
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21M.2.SL.TZ2.2b.i:
Using the letter C, label the stage on the diagram where chromosome supercoiling occurs.
- 21M.1.SL.TZ1.7: A tissue sample was examined under the microscope in order to determine a mitotic index. The...
