8- Stem Cells =)

Question 1

Give two characteristic features of stem cells. (2)

Answer 1

1. will replace themselves/ keep dividing
2. undifferentiated –> develop into other cells

Question 2

Myelodysplastic syndromes (MDS) are a group of malignant cancers. In MDS, the bone marrow does not produce healthy blood cells.
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. (3)

Answer 2

• ↓ methylation of DNA
• tumour suppressor genes expressed
• prevents rapid uncontrollable cell division

Question 3

Suggest how the growth of new blood vessels into damaged heart tissues could increase the rate of repair of tissues. (3)

Answer 3

• ↑ blood supply
• brings ↑ O2 + glucose for resp.
• ↑ a.a. for protein synth.
• for cell repair

Question 4

Induced pluripotent stem cells (iPS cells) are a new type of stem cell.
To produce iPS cells, four genes that code for different transcription factors are added to the genome of somatic (body) cells. The transcription factors produced cause the somatic cells to be converted into iPS cells.
Suggest why it may be better to produce differentiated cells from iPS cells than from pluripotent stem cells
(2)

Answer 4

1. x ethical issues ∵ x embryos used
2. x immune response w/ iPS cells
3. limited supply of embryos
4. iPS cells ✔ used in same individual that provided somatic cells

Question 5

Scientists used four transcription factors to reprogramme skin cells to form iPS cells.
Suggest how transcription factors can reprogramme cells to form iPS cells. (2)

Answer 5

• attach to promoter region
• stimulate transcription