Stem Cells/ Epigentics

Question 1

Pluripotent stem cells

Answer 1

able to give rise to many types of specialised cells, but not placental cells.

Question 2

Toti potent stem cells

Answer 2

can give rise to all / any types of specialised cells, including placental cells.

Question 3

Stem cell definition

Answer 3

An undifferentiated cell that can give rise to specialised cells that can divide to provide more stem cells.

Question 4

Describe the stages of a stem cell differentiating into a specialised cell/ gene expression

Answer 4

1. The stem cell receives a signal
2. The specific gene is activated
3. RNA polymerase binds to the promoter on DNA
4. Transcription occurs to produce mRNA
5. Translation occurs to make a specific protein
6. Relate protein to exam question (e.g haemoglobin if specialised cell is a red blood cell).

Question 5

DNA methylation

Answer 5

Methyl groups attach to DNA bases, stopping transcription. This stops RNA polymerase from binding to the promoter as the gene is not activated.

Question 6

Histone modification (acetyl)

Answer 6

Affects how tightly DNA wraps around histones. When tightly wrapped, the genes aren’t active and cannot be transcribed as it stops RNA polymerase from binding to the promoter.

Question 7

Operon definition

Answer 7

A section of DNA contained by an operator (promoter)

Question 8

Describe the effect of lactose on the lac operon

Answer 8

Lactose allows the lac operon to function, it binds to the repressor, allowing RNA polymerase to bind to the promoter, allowing transcription to make mRNA to produce beta galactosidase.