AQA AS Biology

Topic Questions

2.3 Cell Division in Eukaryotic & Prokaryotic Cells

1a1 mark

Figure 1 below shows a representation of the events that take place during the cell cycle. 

Figure 1

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Name the stage of the cell cycle that contains G1, S and G2.

1b3 marks

State three cellular processes that take place during G1 of the cell cycle.3DQCx70i_1

1c1 mark

Before the cell progresses from G1 into S phase, it needs to pass through a stage called the G1/S checkpoint, which prevents the cell cycle from proceeding if certain conditions are not met. Suggest one reason why the cell might not progress through the G1/S checkpoint. 

1d1 mark

The M phase of the cell cycle in Figure 1 involves cell division by mitosis. The frequency of mitosis depends on the length of time that the cell spends completing each cell cycle. 

A human cell takes 12 hours to complete one cell cycle. Calculate how many cells will be present if the cell cycle proceeds at a constant rate for 4 days.

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2a4 marks

Fill in the gaps labelled i - iv in the following paragraph. The gaps may just contain one word or may contain a series of words.

Mitosis is a process during which cell nuclei divide to produce ___(i)___ new daughter nuclei. These cells are ___(ii)___ to each other and to their parent cell and contain ___(iii)___ chromosomes. After nuclear division, the cell cytoplasm divides by ___(iv)___. 

2b2 marks

State and explain two functions of mitosis.

2c1 mark

Figure 1 below shows the stages of mitosis in the incorrect order.

Figure 1

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Number stages A, B, C and D from Figure 1 with the numbers 1 - 4 to indicate the order in which they occur in mitosis. 

2d2 marks

Name stage C shown in part (c) above, and state one event that occurs during stage C.

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3a4 marks

 Figure 1 below shows multiple cells at different stages of the cell cycle.

Figure 1

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Identify the stages of the cell cycle taking place in cells A-D in Figure 1

3b2 marks

Describe the events taking place in cell D of Figure 1.

3c1 mark

State how you were able to identify the stage of the cell cycle shown in cell B of Figure 1.  

3d1 mark

Use the information provided by the scale bar in Figure 1 to calculate the magnification  of the image. 

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4a3 marks

A student wanted to observe cells during mitosis, and decided to follow the method described in Figure 1 below:

Figure 1

  1. Cut 1 cm from the tip of a growing root.
  2. Place the cut root tip in a test tube containing 1 M hydrochloric acid. The test tube should be placed in a water bath at 60°C for 5 minutes.
  3. Remove the root tip from the test tube and rinse with distilled water. Dry carefully with a paper towel.
  4. Remove 2 mm from the very tip of the root sample and place on a microscope slide.
  5. Break the 2 mm root tip apart and spread the cells out using a mounted needle.
  6. Add a few drops of toluidine blue stain.
  7. Lower a cover slip over the root tip sample. Place a paper towel over the cover slip and press down gently, being careful not to break the cover slip or move it sideways.
  8. Observe the slide using an optical microscope.

Explain the reason for steps 1 and 7 in Figure 1

4b1 mark

One of the root tip samples observed by the student is shown in Figure 2 below.

Figure 2

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State the number of cells in the sample shown in Figure 2 that are undergoing metaphase.

4c2 marks

For another root sample, the student counted the number of cells that were in each stage of the cell cycle. Their results are shown in Table 1 below.

Table 1

Stage of the cell cycle

Number of cells

Interphase

43

Prophase

19

Metaphase

7

Anaphase

5

Telophase

9

Use the information provided in Table 1 to calculate the mitotic index for this root tip sample.

4d2 marks

A medical test might involve the calculation of a mitotic index. Explain the potential significance of an abnormally high mitotic index in a tissue sample.

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5a4 marks

Table 1 below contains some information about cell division in eukaryotic and prokaryotic cells.

Table 1

Eukaryotic cells

Prokaryotic cells

2 daughter cells produced

2 daughter cells produced

Daughter cells are genetically identical to parent

A

B

Circular chromosome and plasmids are replicated

Carry out mitosis

C

Nuclear membrane breaks down during cell division

D

Use your knowledge of cell division to fill in the gaps in Table 1 marked A-D.

5b2 marks

The method of prokaryotic cell division shown in Table 1 is also used by a group of eukaryotic cells called the protozoans.

A student wanted to observe the method of cell division used by prokaryotic cells under an optical microscope and decided to use a protozoan called an amoeba. Their specimen is shown in Figure 1 below.

Figure 14

Use information from Figure 1 and your own knowledge of microscopy to suggest why the student decided to use amoeba rather than bacteria to observe this method of cell division.

5c2 marks

The scale bar shown in Figure 1 was calculated by the student. Describe how the student could have used the eyepiece graticule of the microscope to measure the size of the amoeba.

5d1 mark

State one way in which viral replication is different from both of the processes described in Table 1 in part a) above.

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1a5 marks

During interphase in eukaryotic cells, DNA replication takes place. Explain why one strand of DNA replicates continuously, whereas the opposite strand replicates discontinuously. 

1b4 marks

Some cell biologists believe that use of the term ‘cell division’ should be discontinued and replaced with ‘cell multiplication’. Evaluate this claim using your knowledge of the cell cycle.

1c2 marks

A team of researchers estimated the numbers of cells in different stages of the cell cycle in healthy, growing onion plants. They took two tissue samples, A and B, from different parts of a plant. One tissue sample came from a root tip, the other from a large leaf near to the bottom of the plant’s stem. Their results are shown in Table 1.

Table 1

Stage of the cell cycle

Tissue A / number of cells counted

Tissue B / number of cells counted

Interphase

779

559

Metaphase

36

165

Prophase

57

178

Anaphase

44

115

Telophase

42

88

Total

958

1,105

In tissue sample B, a full cell cycle took 20 hours and 45 minutes. Calculate the time, in minutes, that these cells were in telophase during one cell cycle. Show your working. 

1d2 marks

Identify which tissue sample, A or B, was taken from the root tip. Use the information in Table 1 to explain your answer. 

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2a3 marks

Eukaryotes all possess a haploid number of chromosomes, denoted as n. The value of n varies from species to species. 

Chickens have n = 39.

Complete Table 1 below as it applies to chickens.

Table 1

Stage of the Cell Cycle / 

Type of cell

Number of chromosomes contained in a cell

At beginning of cell cycle

Somatic cell

 

G1 stage of interphase

Somatic cell

 

G2 stage of interphase

Somatic cell

 

After cytokinesis

Somatic cell

 

-

Gamete

 

2b1 mark

A chicken has approximately 40% of the DNA of a human in its genome, whereas it possesses a higher haploid number of chromosomes (n = 39, versus n = 23 for humans). Explain this apparent contradiction. 

2c4 marks

Describe and explain the factors that influence the duration of the cell cycle in multicellular organisms. 

2d3 marks

The human genome contains 2.9 x 109 base pairs. The S phase of a particular fast-growing cell type lasts 8 hours. Given that DNA polymerase has a replication rate of 40 nucleotides s-1  enzyme  molecule-1, calculate the number of DNA polymerase molecules in operation during S phase. State your answer to an appropriate number of significant figures. 

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3a2 marks

A researcher prepared a stained squash sample of cells from the tip of a garlic root. The first 3 mm of a root tip was cut off and stained on a microscope slide, before placing a coverslip on top of the sample and stain. She then examined the sample under a light microscope. 

During the sample preparation, the researcher pressed down on the sample tissue by applying pressure to the coverslip. Explain why this step was taken. 

3b2 marks

The researcher drew a picture of what she could see in the field of view of the microscope. This is shown in Figure 1.

Figure 1

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Using Figure 1, calculate the mitotic index of the garlic root tip tissue. 

3c2 marks

This researcher’s colleagues calculated that the cell cycle of garlic root tips in growth is 1,320 minutes in length, and that on average, cells spend 4 hours in the visible stages of mitosis. 

Calculate the percentage difference between the data gathered by this researcher and the mean length of the mitotic stages found by her colleagues.

3d2 marks

Compare and contrast the process of cytokinesis in animal and plant cells. 

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4a3 marks

The cell pictured in Figure 1 is undergoing the prophase stage of mitosis. Identify structures A, B and C and describe how they behave during prophase. 

Figure 1

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Label

Name of structure

Behaviour during prophase

A

   

B

   

C

   

4b4 marks

Figure 2 shows the mortality rates in men of various age groups from prostate cancer in Europe from 1980 to 2015.

Figure 2

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Describe and explain the overalls trend shown in Figure 2.

4c4 marks

Using data from Figure 2, compare the percentage improvements in death rates between 1995 and 2015 in men of age groups 60-69 and men aged 80+. Suggest an explanation for the difference you have calculated. 

4d4 marks

Relate the term, ‘metastasis’ with a person’s survival chances following the occurrence of metastasis. 

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5a4 marks

Figure 1 shows a scanning electron micrograph of a cell from the bacterial species Bacillus subtilis undergoing binary fission. 

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Compare and contrast the processes of binary fission and eukaryotic cell division. Do not include references to meiosis in your answer. 

5b4 marks

Under certain laboratory conditions, scientists grew a culture of Bacillus subtilis which was found to replicate once every 46 minutes. A small colony of cells was inoculated into a sterile nutrient broth which contained sufficient food, water and other nutrients to facilitate logarithmic growth of the bacterial cells. These cells entered a lag phase of one hour with no growth before growing logarithmically.

The scientists estimated a total cell count of 1.13 x 1013 cells 24 hours after inoculating the broth. Calculate the number of viable cells in the initial inoculum. Give your answer to 3 significant figures. 

5c6 marks

Evaluate the claim that viruses are not living organisms. Use your knowledge of viral replication to support your answer. 

5d2 marks

Gene therapy involves the introduction of functional genes into cells in place of genes that have become defective and non-functional. Explore the properties of viruses that make them a good candidate for gene therapy. 

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1a1 mark

The death rate from malignant brain tumours was investigated in the UK. The graph in Figure 1 shows the results for women in different age groups.

Figure 1

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Describe the relationship seen in the graph in Figure 1.

1b2 marks

Give two possible explanations for the relationship seen in Figure 1.

1c3 marks

There are two main forms of tumours (one being malignant tumours).

i)
 State the other main form of tumour.



ii)
 Give two ways in which a malignant tumour differs from the other main
form of tumour.
1d2 marks

Benign tumours can still cause damage to the body. Describe two ways in which this can occur.

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2a3 marks

A student is confused by two similar terms they learnt about in class: ‘chromosome’ and ‘chromatid’. They can no longer remember the difference between the two terms. 

The student asks you for help.

i)
 Describe what chromosomes are.

ii)
 Describe what chromatids are.



2b3 marks

A student writes the statements below describing the different stages in mitosis but is missing some information. 

Stage 1: Chromosomes become shorter and thicker, and the nuclear membrane breaks down.

Stage 2: Chromosomes line up along the equator of the cell and ______,

Stage 3: ______, causing the chromatids to separate and move towards ______ .

Stage 4: A new nuclear membrane forms around each group of chromosomes.

Help the student by completing:

i)  Stage 2.

 

ii) Stage 3

2c4 marks

Compare what happens during cytokinesis in animal cells and plant cells.

2d1 mark

Mitosis produces clones.

In simple biological terms, define what clones are.

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3a4 marks

Table 1 below shows features of meiosis and mitosis.

Table 1

Feature

Meiosis

Mitosis

(Homologous) chromosomes associate in pairs

 

 

Crossing over occurs

 

 

Two offspring cells produced

 

 

Initial duplication of parent cell’s DNA content

   


Complete
Table 1 with ticks (✔) where a feature is present.

3b4 marks

The letters F, G, H, I and J represent the stages of mitosis.

F = interphase

G = prophase

H = metaphase

I = anaphase

J = telophase

Decide which one of the letters, F to J, the following statements refer to.

(i)
Two nuclear envelopes form.
(ii)
The nuclear envelope disappears.
(iii)
After this stage is complete, the chromatids can now be referred to chromosomes.

(iv)   DNA is replicated.

3c2 marks

The diagram in Figure 1 shows two chromosomes in a cell undergoing mitosis.

Figure 1

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Regarding the diagram in Figure 1:

(i)
What do P, R and S represent?

(ii)
What will happen to Q during anaphase?
3d2 marks

After looking at the diagram in Figure 1, a scientist concludes that the two chromosomes in Figure 1 are homologous.

Use the diagram in Figure 1 to explain why the scientist has come to this conclusion.

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4a4 marks

Figure 1 shows a micrograph of cells in actively dividing tissue from the tip of a plant root.

Figure 1

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i)Name the process by which many of the cells in Figure 1 are dividing.

ii)  Using Figure 1, complete Table 1

Table 1

Cell

Name of the stage of cell division

W

 

V

 

Z

 
4b3 marks

Regarding Figure 1:

i)

In which of the cells (U, V, W, X, Y or Z) can vesicles now fuse to form new cell membranes across the cytoplasm in order to separate the cell into two daughter cells.

ii)

What stage of cell division are these cells in?

4c2 marks

The mitotic index is a measure of the proliferation status of a cell population (i.e. the
proportion of dividing cells).

i)
A student prepared a root tip squash and observed the cells under a microscope. A total of 147 cells were observed and 95 of these cells were observed in various stages of mitosis.

Calculate the mitotic index for this dividing root tissue.

ii)
The teacher wanted to double-check this. The student had counted the total number of cells correctly but the teacher calculated a mitotic index of 81.

Calculate the number of cells undergoing mitosis that the teacher observed.

4d1 mark

When the student prepared the root tip squash in part c), the root tip was placed on a microscope slide with a stain.

Explain why a stain was used.

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5a5 marks

Explain how genetic variation is increased through meiosis.

5b1 mark

The diagram in Figure 1 shows a cell cycle.

Figure 1

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What does the part of the cell cycle labelled I in Figure 1 represent?

5c1 mark

Skin cells complete the cell cycle in a short time.

Give one advantage of this.

5d2 marks

The average time required for a human skin cell to complete the cell cycle is 2 hours 48 minutes.

Calculate the time required in minutes for one skin cell to multiply to produce 16 cells.Show your working 
.

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