Spaced patterns

Question 1

Why should cells be produced in proportion to each other?

Answer 1

1. To ensure that all the different organs are produced.
2. To ensure organs are an appropriate size for their function.
3. To ensure a particular organs is not inappropriately sized compared to another.

Question 2

Four spaced pattern examples

Answer 2

Feathers
Drosophila sensory bristles
Xenopus primary neurogenesis
Plant trichomes

Question 3

How are spaced patterns produced?

Answer 3

Lateral inhibition

All cells have potential but only one will actually do it i.e. 1 cell becomes nervous system, others become epidermis.

Question 4

How can you ensure that only one cell will adopt the primary cell fate and not all of them?

Answer 4

Once one cell is stimulated it releases inhibitory signals to stop neighbouring cells from adopting the same fate. If you kill a cell, a neighbouring cell will take over the fate.

Question 5

What 4 cells are sensory bristles on Drosophila made of?

Answer 5

1. Shaft cell
2. Neurone- connects bristles to NS
3. Sheath cell- glial- helps electrical conduction
4. Socket cell

Question 6

What are the two classes of genes that affect bristle development?

Answer 6

Proneural- fail to make bristles

Neurogenic- make too many bristles- failure in lateral inhibition (Notch, delta).

Question 7

What are mosaics?

Answer 7

Small groups of cells which are mutant, inside a wild type background

Question 8

Signal and receptor protein rules

Answer 8

If you take out receptor, it only matters if it’s from the receiving cell.
If signal is mutated in the receiving cell then development is normal.
If signal is mutated in the signalling cell then development is mutated.
Vice versa.

Question 9

Which one is the receptor and which is the signal: notch or delta? What are they necessary for?

Answer 9

Notch=receptor
Delta=signal
Notch is required for lateral inhibition
Delta is required for signalling

Question 10

Examples of proneural mutant genes.

Answer 10

achaete

scute

Question 11

What are the genes in the two classes of mutants which affect trichome development?

Answer 11

No trichomes: Glabra1, TTG1, Glabra3- form transcriptional complex (turn on Glabra2)
Too many trichomes: Tripychon, Caprice- form non-functional complex with Gl2 and TTG1.

Question 12

What are morphogens?

Answer 12

A molecule that defines two or more cell fates at different concentrations.

Question 13

In the development of the vulva in C.elegans, what does the anchor cell do?

Answer 13

Sends out signal to make vulva from the P cells.

Question 14

Which P cells actually make the vulva?

Answer 14

P6p- primary
P5p and P7p- secondary
Others can make it too if you kill P5p-P7p.

Question 15

What is the signal from the anchor called and what is it detected by?

Answer 15

The signal is Lin3 which is a TGFa

The receptor is Let23 which is a RTK.

Question 16

What happens if you remove Lin3 and Let23?

Answer 16

If you remove Lin3 from anchors, development fails.

If you remove Let23 from all P cells, development fails.

Question 17

What does the concentration of Lin-3 dictate?

Answer 17

The primary, secondary and tertiary cell fates:
Hight conc=primary
Moderate conc=secondary
Low conc=tertiary

Question 18

What do mutations in the lin-12 gene cause?

Answer 18

Loss of function: get 2 anchor cells and 2 primary cells
Gain of function: P6p becomes primary cell, the rest become secondary- too many secondary.

Lin12 drives towards secondary cell fate.

Question 19

What is morphogenesis?

Answer 19

Taking on a new shape.

Question 20

What is epiboly?

Answer 20

Thinning and spreading of cell layers

Question 21

What is convergence extension?

Answer 21

Narrow along one axis and elongate