AQA GCSE Biology: Combined Science

Topic Questions

1.2 Cell Division

1a5 marks

Complete the sentence using the correct words from the box.

A chromosome is a threadlike structure found in the nucleus of a _____________ cell. In a __________ human body cell, there are ______ pairs of chromosomes.  The ___________ of an organism is determined by the combination of _______ (different versions of genes) that are inherited from each parent.

DNA 46 Allele Phenotype Gene
Eukaryotic Haploid Diploid Prokaryotic 23

1b1 mark

A diploid nucleus from the body cell of a dog contains 78 chromosomes. 

How many chromosomes would be found in the nucleus of a dog's gamete?

1c1 mark

Figure 1 shows a cell preparing for mitosis.

Figure 1
visible-chromosomes-mitosis-1

Which of the following statements indicates that the cell in Figure 1 is preparing to divide?

  • The nucleus has visible pores

  • The nucleus is visible and 'X' shaped

  • The chromosomes are visible

  • There is a haploid number of chromosomes

1d3 marks

Identify the three stages of the cell cycle.

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2a1 mark

State why mitosis is important in multicellular organisms.

2b
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1 mark

Figure 2 shows the nucleus of a male gamete from a frog.

Figure 2

sperm-1

What is the diploid number of chromosomes for a body cell in a frog?

2c4 marks

Complete the table to identify which statements about mitosis are true and which are false.

Table 1

Statement True False
Mitosis produces genetically identical cells    
A cell divides twice in the process of mitosis    
Daughter cells from mitosis are haploid    
DNA is replicated before a cell can divide    

2d2 marks

Most human cells that divide by mitosis are specialised to carry out a particular function. This is because the parent cell from which they originated was already differentiated.

Give the name of these cells and state where they might be found in the human body.

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3a2 marks

Give the definition of a stem cell.

3b1 mark

Which of the following statements about stem cells is not true?

  • Meristem cells can differentiate into any type of plant cell throughout the life of the plant

  • Adult stem cells are partially specialised

  • Umbilical cord stem cells can develop into any of the different cell types in the human body

  • Embryonic stem cells could be used to cure type 1 diabetes

3c1 mark

Identify the process shown in Figure 3.

Figure 3

human-cloning-1

3d2 marks

Identify two cells from Figure 3 which would contain a diploid number of chromosomes.

3e2 marks

Explain why the production of stem cells as shown in Figure 3 is opposed by many people.

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4a2 marks

Below is a list of statements regarding use of stem cells from plants.

A - Clones can be produced quickly
B - Populations of species under threat can be cultivated
C - There will be low genetic diversity in the cloned plants

D - Crops with resistance to pests can be cloned 

Table 2

Advantages Disadvantages
   

Write the letter of each statement in the correct column of Table 2 to show whether it is an advantage or a disadvantage of stem cell use.

4b1 mark

State the location of the stem cells in plants.

4c3 marks

Identify the correct labels from the words provided to complete the diagram in Figure 4

Figure 4

stem-cells-labels-1
White Blood Cell Red Blood Cell Embryonic Stem Cell
Meristem Egg Cell Adult stem Cell

4d1 mark

Which statement correctly explains the label given to cell Z in Figure 4 from part (c)?

  • Cell Z produces antibodies

  • Cell Z is found in a 5 day old embryo

  • Cell Z is a haploid cell

  • Cell Z is partially differentiated in the bone marrow 

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5a1 mark

Figure 5 shows the cycle of a cell which lasts 10 hours in total. 

Figure 5

cell-cycle-1

How long does stage 2 last?

5b2 marks

Stage 1 in Figure 5 represents mitosis in the cell. 

The statements in Table 3 describe the process of mitosis.

Table 3

Statement

Number order

(1 - 4)

Two genetically identical daughter cells are produced  
Chromosomes are pulled to either end of the cell  
Cytoplasm splits  
Cell growth and DNA replication occurs  

Place the statements in the correct order (1 = first, 4 = last).

5c1 mark

Describe one use of plant stem cells.

5d2 marks

Draw a line to link each stem cell type in Figure 6 with the associated issue that they might involve.

Figure 6
stem-cells-issues-2

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1a2 marks

Figure 1 shows the quantity of DNA found in the nucleus of a human cell throughout the cell cycle.

Figure 1
dna-quantity-mitosis-adjustment-1

Identify what is happening during stage B on Figure 1. Explain your answer.

1b
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3 marks

Figure 1 shows two complete cell cycles. 50% of the cell cycle is spent in stage A and 30% is spent moving through stage C

Calculate how long the cells spend in stage B of the cell cycle.

1c1 mark

How many chromatids would be found in the nucleus of this human cell during stage B?

1d6 marks

Describe the stages of the cell cycle.

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2a3 marks

When a cell divides by mitosis, it produces identical daughter cells, however, when a zygote divides by mitosis, it develops into an embryo and then a foetus.

Explain how the process of mitosis can produce a whole organism from a single cell.

2b6 marks

Compare and contrast the processes of mitosis and meiosis.

2c
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3 marks

Initially, before a cell can divide, it needs to prepare for division by replicating DNA within the nucleus. During this time, there are no visible chromosomes. 

Figure 2 shows a cell sample taken from plant tissue. The cell cycle in this plant tissue takes 20 hours.

Figure 2

calculating-stages-of-the-cell-cycle-1

Calculate how long cells remain in the preparation stage before cell division occurs.

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3a6 marks

Multiple sclerosis (MS) is a condition which affects the central nervous system caused by the immune system mistakenly attacking the brain and nerves. MS can lead to symptoms which flare up periodically, such as fatigue, vision problems, muscle spasms, mobility problems, difficulty in thinking, learning or planning, amongst others.

There are several different treatments for MS; two are considered here.

  1. Stem cell treatments:  Healthy cells found in the patients bone marrow can be used to rebuild the immune system. Must be used in combination with chemotherapy to remove the harmful immune cells.
  2. Disease modifying therapies (DMT): Medicines that can reduce the number of relapses a patient suffers and reduce the symptoms of MS. An example of a DMT is a drug called Lemtrada.

Table 1 gives some extra information about these two treatments for MS.

Table 1

Treatment type Side effects Cost Success rate
Stem Cells

Risk of developing infections, cancer or fertility issues

Chemotherapy may lead to fatigue and appetite loss, hair loss

1 in 330 people may die

$550 000 per treatment

94% success rate (condition stabilised) over 4 years

Can provide a cure for MS

Disease modifying therapies (e.g. Lemtrada)

Headaches, rashes, nausea, under or overactive thyroid, changes in blood pressure or kidney problems

$340 000 for 5 years of treatment

82% success rate (condition stabilised) over 4 years.

Does not provide a cure.

Evaluate the use of stem cells and disease modifying therapies to treat multiple sclerosis.

3b4 marks

Heart attacks may be caused if a coronary artery becomes blocked and the flow of oxygenated blood is restricted. This can result in damage to the heart muscle tissue.

Suggest how embryonic cells could be used to treat a patient after a heart attack.

3c2 marks

A patient who has suffered a heart attack was offered treatment using stem cells from an embryo, but refused due to the use of embryonic stem cells.

Suggest a reason for this decision.

3d4 marks

The patient mentioned in part (c) was offered treatment using their own healthy stem cells removed from their heart tissue.

Evaluate the decision to use these stem cells as an alternative to embryonic stem cells in the treatment of the damaged heart tissue.

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4a
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4 marks

Some scientists studied mitosis in yeast cells. Figure 3 shows the concentration of DNA and the number of yeast cells over a 12 hour period.

Figure 3

yeast-cell-mitosis-3

Describe and explain the shape of the curve for the number of yeast cells between 2 and 8 hours.

4b
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2 marks

Onc cell cycle in Figure 3 from part (a) takes 6 hours.

Calculate the percentage of time taken by mitosis in one cell cycle.

4c4 marks

Figure 4 shows cells in two stages of division.

Figure 4

mitosis

Describe the changes that occur in the cell between image X and image Y.

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5a
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4 marks

Cancer cells originate from healthy cells where the cell cycle is not being controlled normally. This can lead to uncontrolled cell division and the formation of tumours. Drugs used to destroy cancer cells also cause damage to healthy cells, although are more effective against the cancer cells.

Figure 5 shows the effect of a chemotherapy cancer treatment on the number of healthy and cancerous cells over a 12-week time period.

Figure 5

cancer-cell-mitosis-1

Calculate how many more cancer cells than healthy cells were destroyed after the first treatment.

Give your answer in standard form.

5b1 mark

With reference to the data in Figure 5, identify a time period in which the cancer cells were dividing by mitosis. 

5c2 marks

Another treatment for cancer patients is to receive a stem cell transplant from a donor. The process includes the following steps:

  1. The patient is given a high dose of chemotherapy
  2. Stem cells are taken from the bone marrow of a closely-related individual (with similar tissue type and genotype)
  3. Stem cells are introduced into the patient
  4. The patient is monitored for after-effects of the transplant

With reference to the data in Figure 5 and the information provided here, suggest why a high dose of chemotherapy might be necessary.

5d1 mark

With reference to the process described in part (c), suggest an issue that might be associated with receiving a stem cell transplant which requires careful monitoring of the patient after the procedure (stage 4).

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1a1 mark

Figure 1 below is a photomicrograph of cells in the root of an onion.

Figure 1 mitosis-Onion cells

On the image above, label a cell that is actively dividing with the letter X.

1b1 mark

Name the type of cell division that occurs in the meristem of plants for growth.

1c1 mark

Before a cell divides, what must happen to its genetic material?

1d2 marks

A group of students decided to investigate the cell cycle.

They prepared a microscope slide of a root tip from an onion.

They then visualized the slide under a light microscope to count the number of cells in each stage of the cell cycle in one field of view.

The table below shows their results.

Stages in the cell cycle

 

Non-dividing cells

Stage 1

Stage 2

Stage 3

Stage 4

Total

Number of cells

36

15

9

6

2

68

Different stages of the cell cycle take different amounts of time.

Which stage of the cell cycle is the slowest?

Give a reason for your answer.

1e3 marks

It takes 18 hours for one complete cell cycle in a typical onion root tip cell.

Calculate the length of time Stage 3 lasts in a typical onion root tip cell.

Give your answer to 2 significant figures.

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2a3 marks

Read the information below about stem cells:

It may be possible to treat some human diseases, such as Parkinson’s and diabetes, with stem cells in the future.

Human early embryos produced in vitro are a source of stem cells.

The use of embryonic stem cells to treat human disease is new and patient trials have already begun.

Another source of stem cells is adult bone marrow.

The operation for collecting these cells is simple but it can be painful. It is already possible to use adult stem cells to treat certain blood diseases.

There is also hope that adult stem cells from bone marrow can also be used to treat other diseases such as heart disease; such trials have already begun.

Explain how an embryonic stem cell differs from an adult stem cell.

2b5 marks

Evaluate the use of embryonic and adult stem cells to treat human diseases.

Your answer should contain a conclusion.

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3a1 mark

How many pairs of chromosomes are there in a body cell of a human?

3b2 marks

For any organism to grow, it must be capable of making new cells.

Describe what must happen in a cell before it can divide.

3c3 marks

Outline the process by which a cell divides by mitosis.

3d2 marks

Why is cell specialisation (differentiation) an important process in the development and growth of a fertilised egg into a healthy baby?

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4a2 marks

After a baby is born, it is possible to use the umbilical cord as a source of stem cells.

What are stem cells?

4b1 mark

In Vitro Fertilisation can be used to produce embryos for research purposes. Stem cells can be extracted from a 3-day-old embryo made in this way.

Suggest why it may be considered more ethically acceptable to take stem cells from an umbilical cord rather than an embryo.

4c1 mark

Stem cells taken from an umbilical cord can be frozen and stored. They could be used later in that child’s life to treat a condition.

Suggest a reason why it would be better to use a child’s own umbilical cord stem cells instead of stem cells donated from another person.

4d4 marks

Figure 2 below outlines the process of therapeutic cloning.

Figure 2

human-cloning

This technique could be used to produce cells to treat conditions such as paralysis or diabetes, or to produce a baby.

Scientists may be allowed to use therapeutic cloning to treat disease but not to produce a baby.

Using information from the diagram and your own knowledge, suggest an explanation for this.

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5a1 mark

The nucleus of a typical onion cell contains 16 chromosomes.

What is a chromosome?

5b1 mark

An onion cell divides by mitosis.

How many chromosomes will each of its daughter cells contain?

5c2 marks

Figure 3 shows a photograph of an onion cell at one point during the cell cycle.

Figure 3

onion-cell-mitosis

Describe what is happening to the cell in Figure 3.

5d2 marks

Suggest the events that would occur after those observed in the cell in Figure 3.

5e2 marks

Onion plants contain meristem tissue.

Compare the meristem tissue found in an onion plant with bone marrow tissue found in humans.

5f2 marks

Many plants are at risk of extinction as a result of human activity.

Stem cells from the meristem can be used to clone rare plant species.

Outline the advantages of cloning plants in this way.

5g1 mark

Suggest one other useful application of cloning plants. 

5h1 mark

Suggest one disadvantage of producing clones of plants from meristems.

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63 marks

Embryonic stem cells have the potential to be used to treat many human diseases.

Suggest how embryonic stem cells could be used to treat a person who has been paralysed.

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