Cell differentiation T3

Question 1

The scientists have suggested that epigenetic events are involved in regulating collagen
synthesis in rats given alcohol.
Explain how epigenetic events might be involved in regulating collagen synthesis in rats given
alcohol.
(2)

Answer 1

• Exposure to alcohol may result in changes of methylation of DNA/ modification of histones.
• So that collagen gene is more likely to be expressed/ activated/ transcribed.

Question 2

State what is meant by the term stem cell.

2

Answer 2

• A cell that is undifferentiated.
• That can give rise to specialised cells.
• That can divide to produce more stem cells.

Question 3

Compare and contrast the results of mitosis and meiosis.

3

Answer 3

• Both increase the number of cells.
• Mitosis produces diploid cells, and meiosis produces haploid.
• Meiosis produces genetically different cells, whereas mitosis produces genetically identical cells.

Question 4

Type 1 diabetes occurs when beta cells in the pancreas do not produce insulin.
Stem cells produced from skin cells can be used to replace these beta cells in mice. The skin
cells can be stimulated to become pluripotent stem cells.
The pluripotent stem cells were injected into the mice. After eight weeks, these cells had
developed into insulin-secreting beta cells.
Describe how these pluripotent stem cells became specialised beta cells.
(4)

Answer 4

• Stimulus i.e. chemical.
• Some genes switched on/active/expressed.
• Transcription/mRNA of active gene.
• mRNA is translated to produce protein.
• Protein modifies cells, protein determines cell structure/function.

Question 5

What are pluripotent stem cells?

Answer 5

unspecialised cells that can differentiate to give rise to almost any type of cell in the body, excluding totipotent cells.

Question 6

It is thought that an increase in shell pigmentation levels provides protection against UV
light. UV is a form of radiation that can damage DNA.
Explain how the DNA of the snail could be damaged.
(2)

Answer 6

• Interferes with DNA replication.

- Potentially leading to mutations.

Question 7

Recently, scientists have shown an interest in using plant tissue culture techniques to
produce large numbers of genetically identical cotton plants. Cotton plants provide fibres used
for clothing.
Plant tissue culture techniques depend on the totipotent properties of the cells used.
(a) Describe how you could use a plant tissue culture technique to show totipotency in cotton
plant seedlings.
(4)

Answer 7

• Use part of the seedling.
• Use agar.
• Agar contains growth substances/hormones.
• Using aseptic technique.
• Cover top of container to prevent contamination.
• Supply light.
• Give 1-6 weeks for growth.
• Look for root/leave formation.

Question 8

Human stem cell research involves the use of both totipotent and pluripotent stem cells.
Describe the differences between a totipotent stem cell and a pluripotent stem cell.
(2)

Answer 8

• Totipotent can give rise to a total human, pluripotent cannot.
• Totipotent can give rise/differentiate into any cell.
• Pluripotent cannot differentiate into any cell in the body.
• Only totipotent can give rise to other totipotent stem cells.

Question 9

Explain how stem cells become specialised and develop into heart muscle cells.
(4)

Answer 9

• Stimulus i.e. chemical or hormone.
• Activation of some genes.
• Only activated genes transcribed/ mRNA made only at active genes.
• mRNA translated on ribosome.
• Protein made.
• Determining cell structure and function. Permanently modifies cell.
• Cell differentiation.

Question 10

Explain the advantages of using stem cells from the patient instead of using stem cells from
a donor.
(2)

Answer 10

• Genetically identical to patient cells.
• No risk of rejection.
• Less risk of infection.
• No need for immunosuppressant drug.