2.3 Stem Cells

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In 2023, there were over 7000 people in the UK awaiting a transplant organ. 

Explain why some transplanted organs are at risk of being rejected by the patient and describe what happens if the organ is rejected.

Scientists are researching ways that stem cells can be used to grow organs. The flowchart in Figure 1 below shows one method currently being researched. Eventually, this organ growth method may replace organ transplants.

Figure 1

Discuss the potential benefits and risks associated with the use of stem cells in medicine.

The diagram in Figure 1 shows where a gardener trimmed a rose bush. Meristem tissue was removed from the plant during this procedure.

Figure 1

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Table 1 below shows the numbers of cells taken from a meristem in different stages of the cell cycle.

Table 1

Use this equation to calculate the mitotic index for these cells.

Mitotic index = 

Give your answer to 3 significant figures.

Research has shown that sweet potato, Ipomoea batatas, has shown resistance to viruses when grown via meristem tissue culture. This method involves taking a sample of meristem tissues from a sweet potato plant, and placing them in a growth medium containing nutrients and auxins. The plants produced will all be genetically identical clones to the original plant. The process from taking the tissues to producing the sweet potato takes 8 weeks inside a science laboratory where conditions can be controlled. Growing sweet potatoes usually takes around 12 to 16 weeks when farmed using traditional methods.

Suggest and explain why using the meristem tissue culture method might result in a higher number of edible sweet potatoes than traditional methods of farming. 

This question is about stem cells.

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Stem cell therapy is a type of treatment being developed which involves the use of stem cells to treat certain medical conditions. 

In recent years, stem cell therapy has been used to help treat arthritis. Arthritis is caused by the wearing down of protective tissue (cartilage) that covers the ends of joints.

Figure 1 shows the number of people with arthritis in France.

Figure 1

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Read the information about stem cells.

Stem cell therapy can be used to treat arthritis. This works by injecting the affected joints with stem cells that can then differentiate into cartilage or bone. The operation to remove the stem cells is simple yet painful, however the treatment injection for arthritis is very quick and it is a non-invasive process meaning it doesn’t require surgery. 

Following the stem cell injection, the patient will need to undergo at least 12 weeks of physiotherapy, and during this time the stem cells will release proteins that slow down cartilage degeneration inside the joint.

The use of stem cells to treat arthritis is relatively new, and so far there have been no large-scale studies to show that it is much more effective than the current treatments available. Some research has shown that there is little new cartilage made following the stem cell injections.

The current treatment for arthritis includes either pain-relief medication, which only provides short term relief, or a joint transplant, which has a long recovery period.

Evaluate the use of stem cell therapy to treat arthritis. Use the information above and your own knowledge of stem cells.

You should give a conclusion to your evaluation. 

Figure 1 shows a cross section of a root of a plant.

Figure 1

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The cells in the meristem of a plant undergo the process of cell division in order to produce new cells.

Compare and contrast the processes of cell division by mitosis and meiosis.

Meristem cells can be used to culture (grow) new plants. This process involves taking a sample of meristem cells from a plant, and placing them in nutrient broth to allow them to grow. 

The graph in Figure 2 shows the results from three separate experiments carried out.

• In the first experiment, the scientist took a sample of meristem cells, left them for 5 days in a hormone bath, before planting them in the nutrient broth
• In the second experiment, the scientist took a sample of meristem cells, left them for 15 days in a hormone bath, before planting them in the nutrient broth
• In the third experiment, the scientist took a sample of meristem cells, left them for 25 days in a hormone bath, before planting them in the nutrient broth

Once planted in the nutrient broth, the scientist stopped the experiment after 16 days and recorded the results.

The graph shows the results from the scientist’s experiments.

Figure 2

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There has been considerable publicity about stem cells and their possible benefits in treating certain conditions. Evaluate the use of stem cells in medicine, highlighting the benefits and drawbacks of using them for treating known medical conditions.

Explain why blood capillary cells would not be formed from a bone marrow stem cell.

Explain why, in a growing root, only one daughter cell from a meristem cell division becomes differentiated. 

Give the main reason why embryonic stem cells are preferred for scientific research over adult stem cells.

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

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.

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.

Figure 1 below outlines the process of therapeutic cloning. 

Figure 1

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.