1.6 - Cell Division

During which stage of mitosis does the nuclear envelope break down?

• A.$\hspace{1em}$ Prophase

• B.$\hspace{1em}$ Metaphase

• C.$\hspace{1em}$ Anaphase

• D$\hspace{1em}$ Telophase

Which statement(s) about mitosis is/are true?

• I.	Sister chromatids are pulled apart during metaphase.
  II.	The nuclear envelope reforms during telophase.
  III.	Chromosomes supercoil and become visible during prophase.

• A.$\hspace{1em}$ I and II only

• B.$\hspace{1em}$ II only

• C.$\hspace{1em}$ II and III only

• D.$\hspace{1em}$ I, II and III

In the micrograph below, which letter points to a cell in anaphase?

[Source: Adapted from Reischig, J. (2014, March 11). File (261 13) pressed; root meristem of onion ... - wikimedia. Wikimedia Commons. Retrieved May 13, 2022, from https://commons.wikimedia.org/wiki/File:Mitosis_(261_13)_Pressed;_root_meristem_of_onion_(cells_in_prophase,_metaphase,_anaphase,_telophase).jpg. Copyright under CC BY-SA 3.0]

A human pancreatic cell divides three times by mitosis. What is the end result of these divisions?

• A.$\hspace{1em}$ Two genetically identical daughter cells.

• B.$\hspace{1em}$ Four genetically distinct daughter cells.

• C.$\hspace{1em}$ Eight genetically identical daughter cells.

• D.$\hspace{1em}$ Sixteen genetically distinct daughter cells.

If a cell with a diploid number of 36 undergoes mitosis, how many chromosomes will be present in each daughter cell after cytokinesis?

• A.$\hspace{1em}$ 36

• B.$\hspace{1em}$ 18

• C.$\hspace{1em}$ 72

• D.$\hspace{1em}$ 9

The image shows a micrograph of a cell.

[Source: Adapted from Reischig, J. (2014, March 11). File: mitosis (261 13) pressed; root meristem of onion ... - wikimedia. Wikimedia Commons. Retrieved May 13, 2022, from https://commons.wikimedia.org/wiki/File:Mitosis_(261_13)_Pressed;_root_meristem_of_onion_(cells_in_prophase,_metaphase,_anaphase,_telophase).jpg. Copyright under CC BY-SA 3.0]

What explains the appearance of the cell in the micrograph?

• A.$\hspace{1em}$ The cell is undergoing interphase.

• B.$\hspace{1em}$ The sister chromatids are being pulled apart.

• C.$\hspace{1em}$ The cell is getting larger.

• D.$\hspace{1em}$ The cell is in metaphase.

The micrograph shows onion cells undergoing mitosis. What is the mitotic index of the cells?

[Source: Adapted from Laurent, E. (2022, July 15). File diagram.svg. Wikimedia Commons. Retrieved November 11, 2023 from https://commons.wikimedia.org/wiki/File: Onion_diagram.svg. Copyright under CC BY-SA 4.0]

• A.$\hspace{1em}$ 0.25

• B.$\hspace{1em}$ 0.9

• C.$\hspace{1em}$ 4

• D.$\hspace{1em}$ 0.02

Which is the correct definition of cytokinesis?

• A.$\hspace{1em}$ Division of the nucleus of a cell to form two identical nuclei

• B.$\hspace{1em}$ Splitting of cytoplasm in a parent cell between two daughter cells

• C.$\hspace{1em}$ Pinching off of a daughter cell from a parent cell

• D.$\hspace{1em}$ The pulling away of the plasma membrane from the cell wall

Which word describes the formation of secondary tumours from primary tumours as a result of the movement of cells?

• A.$\hspace{1em}$ Malignant

• B.$\hspace{1em}$ Carcinoma

• C.$\hspace{1em}$ Benign

• D.$\hspace{1em}$ Metastasis

Which statement is a similarity between cytokinesis in animal and plant cells?

• A.$\hspace{1em}$ A new cell wall is formed.

• B.$\hspace{1em}$ Two daughter cells are formed from one parent cell.

• C.$\hspace{1em}$ A cleavage furrow is formed.

• D.$\hspace{1em}$ Vesicles are used to form two layers of membrane.

[Maximum mark: 16]

1. Explain how mitosis is regulated in cells. [4]
   

2. Describe the stages of interphase and their importance to the process of mitosis. [4]
   

3. Discuss the importance of mitosis to living organisms using named examples. [7]
   

The diagram shows the dominant cyclin/CDK complexes at different time points in the cell cycle. Which cyclin/CDK complex activates DNA replication machinery?

[Source: Adapted from Helena, J. M., Joubert, A. M., Grobbelaar, S., Nolte, E. M., Nel M., Pepper, M. S., Coetzee, M., & Mercier, A. E. (2018). Deoxyribonucleic Acid Damage and Repair: Capitalizing on Our Understanding of the Mechanisms of Maintaining Genomic Integrity for Therapeutic Purposes. International Journal of Molecular Sciences, 19(4):1148. Retrieved April 1, 2022, from https://doi.org/10.3390/ijms19041148. Copyright under CC BY 4.0]

• A.$\hspace{1em}$ Cyclin A/CDK 2

• B.$\hspace{1em}$ Cyclin B/CDK 1

• C.$\hspace{1em}$ Cyclin D/CDK 4

• D.$\hspace{1em}$ Cyclin A/CDK 1

The diagram below shows the concentrations of different cyclins during the cell cycle. Which cyclin is involved in preparing for DNA replication?

[Source: Adapted from CNX OpenStax. (2016, May 27). File: Figure_10_03_02.jpg- wikimedia commons. Wikimedia commons. Retrieved May 13, 2022, from https://commons.wikimedia.org/wiki/File.jpg. Copyright under CC BY 4]

• A.$\hspace{1em}$ Cyclin D

• B.$\hspace{1em}$ Cyclin E

• C.$\hspace{1em}$ Cyclin A

• D.$\hspace{1em}$ Cyclin B

The mitotic index of throat tissues taken from 4 different patients is shown below. Which patient is most likely to have cancerous throat tissue?

If the DNA in a somatic cell is changed in an animal as a result of a mutation, which of the following could most significantly affect other tissues in the animal?

• A.$\hspace{1em}$ Mechanisms involved in the cell cycle are altered.

• B.$\hspace{1em}$ Apoptosis occurs in the cell.

• C.$\hspace{1em}$ A start codon is altered which deactivates a gene.

• D.$\hspace{1em}$ Transcription of one or more genes becomes impossible.

[Maximum mark: 9]

The graph below shows the relative amount of DNA in one cell during one complete cell cycle. Each letter represents one stage of the cell cycle.

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1. 1. State which stage of mitosis or interphase is represented by stage B in the graph. [1]
      

   2. Explain your answer to part (i). [2]
      

   3. Bortezomib is an anticancer medication and arrests cells in the G₂ phase. If a cell shown in this graph began the cell cycle at A with 3 relative units of DNA, and Bortezomib was applied to the cell culture at stage A as well, estimate the relative amount of DNA in the cell at the end of C. [1]
      

2. Explain why the amount of DNA in one cell remains the same in stages C and D. [3]
   

[Source: Reischig, J. (2014, March 11). File (261 13) pressed; root meristem of onion ... - Wikimedia. Wikimedia Commons. Retrieved May 13, 2022, from https://commons.wikimedia.org/wiki/File:Mitosis_(261_13)_Pressed;_root_meristem_of_onion_(cells_in_prophase,_metaphase,_anaphase,_telophase).jpg. Copyright under CC BY-SA 3.0]

3. The diagram above shows cells in different stages of mitosis. Label one cell that is in prophase and one cell that is in anaphase. [2]
   

[Maximum mark: 15]

The mitotic index is an indirect way of measuring plant growth. A study was conducted on white onions (Allium cepa), under controlled conditions in a lab, to investigate the effect of soil pH on the mitotic index of the roots.

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1. Describe the trends shown in the graph. [2]
   

2. Outline how the mitotic index is calculated. [1]
   

3. Discuss whether the data support the hypothesis that onion plants should be grown in soil with a pH of 5.5. [2]
   

4. Suggest how a pH of 9 affects the process of mitosis. [2]
   

5. 1. Explain why measuring the mitotic index in the root is an indirect way of measuring the overall growth rate of the onion plant. [1]
      

   2. Suggest another method, apart from measuring mitotic index, that could be used to measure plant growth. [1]
      

6. State one of the variables that must be controlled to make this experiment valid. [1]
   

The table shows the number of cells in different stages of the cell cycle in four samples of lung tissue from four patients. Which tissue has the lowest mitotic index?

	Interphase	Prophase	Metaphase	Anaphase	Telophase	Total
A.	80	30	4	5	1	120
B.	100	9	1	7	8	125
C.	30	15	5	10	0	60
D.	70	20	4	0	6	100

[Maximum mark: 15]

Studies have shown that genes such as Cyclin Dependent Kinase 3 (CDKN3) are highly overexpressed in cervical tumours.

[Source: Adapted from Barrón, E. V., Roman-Bassaure, E., Sánchez-Sandoval, A. L., Espinosa, A. M., Guardado-Estrada, M., Medina, I., Juárez, E., Alfaro, A., Bermúdez, M., Zamora, R., García-Ruiz, C., Gomora, J. C., Kofman, S., Pérez-Armendariz, E. M., & Berumen, J. (2015). CDKN3 mrna as a biomarker for survival and therapeutic target in cervical cancer. PLOS ONE, 10(9). Retrieved December 6 2022, from https://doi.org/10.1371/journal.pone.0137397 Copyright under CC BY 4.0]

1. Calculate the percentage increase of CDKN3 gene expression in cancerous cervical tissue compared to healthy cervical tissue. Make sure you show your working. [2]
   

Overexpression of CDKN3 in cervical tumours has been associated with decreased survival rates in cervical cancer patients and has been shown to trigger cells to exit mitosis and begin cytokinesis.

[Source: Adapted from Barrón, E. V., Roman-Bassaure, E., Sánchez-Sandoval, A. L., Espinosa, A. M., Guardado-Estrada, M., Medina, I., Juárez, E., Alfaro, A., Bermúdez, M., Zamora, R., García-Ruiz, C., Gomora, J. C., Kofman, S., Pérez-Armendariz, E. M., & Berumen, J. (2015). CDKN3 mrna as a biomarker for survival and therapeutic target in cervical cancer. PLOS ONE, 10(9). Retrieved December 6 2022, from https://doi.org/10.1371/journal.pone.0137397 Copyright under BY CC 4.0]

2. A hypothesis has been proposed that overexpression of CDKN3 in cervical tumours results in an increased chance of patient death. Evaluate the evidence for this using the data given. [2]
   

3. Overexpression of CDKN3 results in increased levels of cell division. Describe how CDKs and cyclins are involved in the cell cycle. [2]
   

4. CDKN3 has been identified as an oncogene. State the definition of an oncogene. [1]
   

c-REL is another gene that has been linked to cervical cancer and its expression is correlated with the expression of CDKN3. Using CRISPR technology, cervical cancer cells have been created that do not express c-REL (c-REL -/-). Expression levels of c-REL were checked using protein analysis.

[Source: Adapted from Slotta, C., Schlüter, T., Ruiz-Perera, L. M., Kadhim, H. M., Tertel, T., Henkel, E., Hübner, W., Greiner, J. F., Huser, T., Kaltschmidt, B., & Kaltschmidt, C. (2017). CRISPR/Cas9-mediated knockout of c-rel in Hela cells results in profound defects of the cell cycle. PLOS ONE, 12(8). Retrieved December 06 2022, from https://doi.org/10.1371/journal.pone.0182373 Copyright under CC BY 4.0]

When c-REL is overexpressed in cervical epithelial cells it results in greater proliferation of cells and the cells spend less time in prometaphase (the phase between prophase and metaphase) compared to healthy cervical cells.

[Source: Adapted from: Resichig, J. (2014, March 11). File: mitosis (261 13) pressed; Root Meristem of onion (cells in ... Wikimedia. Retrieved November 1, 2022, from https://commons.wikimedia.org/wiki/File:Mitosis_(261_13)_Pressed;root_meristem_of_onion(cells_in_prophase,_metaphase,_anaphase,_telophase).jpg Copyright under CC BY 3.0]

5. 1. Looking at the photomicrograph above, identify the stage of the cell cyle that most of the cells are in. [1]
      

   2. Based on the evidence provided, suggest, with a reason, which of the labelled cells would be present in the highest numbers in c-REL -/- cervical cancer cells. [1]
      

cREL-/- cervical cancer cells and cervical cancer cells with high expression levels of c-REL were treated with the chemotherapeutic drug, cisplatin. Both types of cells were exposed to different concentrations of cisplatin over a 21-hour period, and the effects on cell number were analysed.

[Source: Adapted from Slotta, C., Schlüter, T., Ruiz-Perera, L. M., Kadhim, H. M., Tertel, T., Henkel, E., Hübner, W., Greiner, J. F., Huser, T., Kaltschmidt, B., & Kaltschmidt, C. (2017). CRISPR/Cas9-mediated knockout of c-rel in Hela cells results in profound defects of the cell cycle. PLOS ONE, 12(8). Retrieved December 06 2022, from https://doi.org/10.1371/journal.pone.0182373 Copyright under CC BY 4.0]

6. Using the graph above, compare the response of cervical cancer cells that express c-REL and the cells that do not express c-REL (c-REL -/-) in response to exposure to different concentrations of cisplatin. [2]
   

7. Suggest a reason for the different effects that cisplatin has on cervical cancer cells expressing c-REL and those that do not express c-REL (c-REL -/- ). [2]
   

8. Suggest why some c-REL -/- cervical cancer cells have a similar level of cell death to those cervical cancer cells expressing c-REL. [1]
   

9. Deduce whether cervical cancer cells expressing high levels of c-REL and CDKN3 will have a higher mitotic index than those with lower levels of c-REL and CDKN3. [1]
   

When is the concentration of cyclin E the highest during the cell cycle ?

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