Development/Differentiation

Question 1

4 things required for differentiation to occur in eukaryotes

Answer 1

1. sense signal in environment
2. transduce signal for differentiation
3. communicate with others
4. responds as a group
   * to differentiate -> cells initiate a developmental program where specific genes are activated or inactivated

Question 2

dictyostelium discoideum

Answer 2

• soil ameoba, feed on bacteria
• model organism for differentiation

Question 3

d.discoideum life cycle (2 parts)

Answer 3

1. vegetative growth (food is plentiful)
2. differentiation growth (starved state)

Question 4

6 d. discoideum starved/differentiation states

Answer 4

1. loose aggregate
2. tight aggregate
3. tipped aggregate
4. mobile slug (move to high food area)
5. hat and culmination
6. mature fruiting body (**80% of cells are spores while 20% remain stalk **and don’t survive)

Question 5

how does d.discoideum aggregation occur (what signaling molecule)?

Answer 5

• cAMP pulse from pacemaker cell
• neighboring cells gravitate to signal, stop dividing, begin sending a secondary cAMP pulse, and become resistant to cAMP signal
• party analogy (follow noise to find party -> too much noise from too many places = lost)

Question 6

when is d.discoideum cell fate decided

Answer 6

• cell-fate of whether a cell becomes spore or stalk happens at slug state

Question 7

model for how d.discoideum vegetative or development genes are regulated

Answer 7

• veg: pufA inhibits PKAc (PKAc acts to turn on dev genes)
• PKAc expression is controlled by translation
• dev state: YakA inhibits pufA so PKAc inhibits veg genes and turns on dev genes