Module 8 - Gene expression is controlled by a number of features

Question 1

Define stem cells cells

Answer 1

Will keep dividing, undifferentiated

Question 2

Define totipotent cells

Answer 2

Can become any type of cell (onoly very early embryonic stem cells)

Question 3

Define pluripotent cells

Answer 3

Can become many types of cells- found in embryos- can divide in unlimited numbers- used to treat diseases

Question 4

Define multipotent cells

Answer 4

Found in adult- limited

Question 5

Define unipotent cells

Answer 5

Only can differentiate into cardiomyocytes

Question 6

Define induced pluripotent stem cells (iPS cells)

Answer 6

Can now be made from adult body cels (somatic)- genes ‘turned on and off’

Question 7

2 marks

Oestrogen is a hormone that affects transcription. It forms a complex with a receptor in the cytoplasm of target cells. Explain how an activated oestrogen receptor affects the target cell.

Answer 7

1. Receptor / transcription factor binds to promoter which stimulates RNA polymerase
2. Increase transcription

Question 8

1 marks

Oestrogen only affects target cells. Explain why oestrogen does not affect other cells in the body

Answer 8

Other cells do not have the oestrogen receptors

Question 9

2 marks

Steroid hormones are hydrophobic.
Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface membrane.

Answer 9

1. Lipid soluble
2. Diffuse through phospholipid bilayer

Question 10

3 marks

The binding of testosterone to an AR changes the shape of the AR. This AR molecule now enters the nucleus and stimulates gene expression.
Suggest how the AR could stimulate gene expression.

AR= receptor

Answer 10

1. AR is a transcription factor
2. Binds to DNA
3. Stimulates RNA polymerase

Question 11

2 marks

Define what is meant by epigenetics.

Answer 11

1. Heritable changes in gene function
2. Without changes to the base sequence of DNA

Question 12

3 marks

Explain how increased methylation could lead to cancer.

Answer 12

1. Methyl groups could be added to both copies of a tumour suppressor gene
2. The transcription of tumour suppressor genes is inhibited
3. Leading to uncontrolled cell division

Question 13

Tumour suppressor gene

Answer 13

These genes produce proteins to slow down cell division and to cause cell death if DNA copying errors are detected

Question 14

3 marks

MDS can develop from epigenetic changes to tumour suppressor genes. In some patients, the drug AZA has reduced the effects of MDS. AZA is an inhibitor of DNA methyltransferases. These enzymes add methyl groups to cytosine bases.
Suggest and explain how AZA can reduce the effects of MDS in some patients.

Answer 14

1. AZA reduces methylation(of DNA
2. Tumour suppressor gene is transcribed/expressed
3. Prevents uncontrollable cell division