Control of cell differentiation

Question 1

Differentiation

Answer 1

The process by which cells become specialised for a particular function.

Question 2

Cell specialisation

Answer 2

Cells are different from one another with respect to:

• function
• morphology
• proteins expressed
• interaction with the outside world

Question 3

Stages of differentiation

Answer 3

1) Commitment; a stem cell exits the maintenance phase and becomes a progenitor cell
2) Cell division; gene expression is regulated within the progenitor cell during the expansion phase
3) Differentiation; the terminally differentiated cell is specialised for its function

Question 4

Transcription

Answer 4

The production of a primary mRNA transcript of a gene, occuring in the nucleus.

Question 5

Transcription factors

Answer 5

Proteins which regulate gene expression by binding to gene regulatory sequences. They are modular, consisting of a DNA binding domain and an activation domain.

Question 6

Gene regulatory sequences

Answer 6

Sequences of DNA which are involved in gene expression. Promoter sites are located close to a gene, and bind RNA polymerase to initiate transcription. Enhancer sites are located upstream or downstream of a gene, and bind to transcription factors which act together to regulate gene expression.

Question 7

Erythropoeitin

Answer 7

A hormone which acts as a transcription factor, promoting cell survival and differentiation of red blood cells. It stimulates haematopoeitic stem cells in bone marrow, acting on a negative feedback loop in response to the oxygen carrying capacity of the blood.