Lecture 22 - Cell differentiation and gene expression

Question 1

Cell differentiation (1)

Answer 1

The production of different cell types within an organism.

Question 2

Cell determination (4)

Answer 2

The stability of cell determination, even after cessation of any inducing signal.
Transmitted to daughter cells after division.
e.g. different WBCs are all in same environment but they remember what cell type they are.
Stable, complex change.

Question 3

How can cell types become different? (1)

Answer 3

Express different sets of genes.

Question 4

What does gene expression mean? (2)

Answer 4

Synthesis of the product of a given gene - a protein or a functional RNAs.
Involves transcription/translation.

Question 5

Is a change in gene expression always differentiation? (1)

Answer 5

No, there is also modulation.

Question 6

Cell modulation (4)

Answer 6

A simple, reversible change in gene expression, with no change in cell type.
e.g. upregulation of alcohol dehydrogenase in liver cells: a transcriptional change that is reversible and dependent on a continuing external stimulus: e.g. blood alcohol.
Also called adaptation.
Temporary, simple change.

Question 7

How are different cells produced? (3)

Answer 7

Diff species have diff genes.
Cell types in same organism have same characteristics.
e.g. normal somatic cells in human have same 46 chromosomes.

Question 8

Dolly the Sheep (5)

Answer 8

Differentiated sheep cell was fused to cytoplasm of a sheep oocyte (egg cell).
Leading to formation of an embryo, which was implanted into uterus of an ewe = Dolly (1996) - fertile.
This also applies to other things such as frogs/plants/fish.
Humans aren’t cloned due to ethical considerations.
All human cell types contain the genome, except maturing lymphocytes.

Question 9

Pure mammalian cell lines showing differentiation in culture (1)

Answer 9

Myoblasts differentiating and fusing to form skeletal muscle fibres, which fuse into multinucleate cell.