Differentiation

Question 1

Stem cells

Answer 1

• undifferentiated cells
• capacity for self renewal through asymmetric cell division
• capacity to differentiate into mature cells (potency)
• ability for quiescence to enter dormant state

Question 2

Cellular hierarchy

Answer 2

1. Symmetric stem cell division
2. Asymmetric stem cell division
3. Progenitor cell division
4. Differentiation

Question 3

Totipotency

Answer 3

The ability of a single cell to give rise to all the embryonic and extra embryonic cell types

Question 4

Pluripotency

Answer 4

The ability of a single cell to give rise to all of the cell types found in the complete adult organism

i.e. cells of all the germ layers

Question 5

Multipotency

Answer 5

The ability of a single cell to give rise to multiple but not all cell types found in the complete adult organism

i.e. differentiation ability is restricted to certain cell types

Question 6

How does differentiation occur

Answer 6

• cells switch on certain genes and switch off others during differentiation
• the type of cell formed is determined by the pattern of gene expression in the cell

Question 7

Role of transcription factors in differentiation (master regulators)

Answer 7

Expressed at early stages
- induce transcription of various target genes that collectively lead to cell differentiation

Question 8

Determination

Answer 8

Occurs before differentiation
Fate of the cell is already specified at this stage
During embryonic development the fate of the cell is restriced

Question 9

What determines cell fate

Answer 9

Cytoplasmic segregation
Induction

Question 10

Cytoplasmic segregation (asymmetric cell div)

Answer 10

Cytoplasmic factors called determinants that are unequally distributed between daughter cells influence cell fate

Question 11

Induction

Answer 11

Factors that are secreted by neighbouring cells influence cell fate

High concentrations may activate transcription factors that triggers the cascade of cellular differentiation

Question 12

Reversibility

Answer 12

Mature plant cells can be experimentally induced to dedifferentiate to a totipotent state

Dedifferentiated totipotent cells can form an entire new plant
= cloning

Question 13

Somatic cell nuclear transfer

Answer 13

Cytoplasmic environment around the nucleus determines cell fate

No info is lost as the cells differentiate into mature somatic cells
= genomic equivalence