Establishment of Cell Polarity

Question 1

What is a good system for studying the acqusition of cell polarity?

Answer 1

The fucous zygote

Question 2

What shape is the zygote of the fucus at 0 hours?

Answer 2

Apolar (spherical)

Question 3

What shape is the zygote of the fucus at 12 hours?

Answer 3

Pear shaped

Question 4

What happens to the zygote of the fucus at 24 hours?

Answer 4

The first cell division takes place at a right angle to the axis of symmetry

Question 5

What are the two parts of the fucus zygote?

Answer 5

The thalus (The bit bulb bit) and the rhizoid (the wee tail)

Question 6

Name 5 enviromental facotrs involved in determining cell polairity?

Answer 6

1. Light
2. Temperature
3. PH and Salt
4. Electrical gradient
5. Fertilisation

Question 7

How is light involved in estabilishing cell polairity in the fucus?

Answer 7

The Rhizoid develops on the shaded side

Question 8

At which point in the fucus is polairity fixed?

Answer 8

After 12 hours - before that you can move light and it will change the polairity

Question 9

How is feritlization involved in stablishing cell polarity?

Answer 9

When the sperm enters whatever point this is will become the rhizoid

Question 10

How is heat involved in establishing cell polarity?

Answer 10

The rhizoid will grow on the warm side

Question 11

How are ph and salt involved in establishing cell polairity in the fucus?

Answer 11

The rhizoid grows to the alkaline ph and the higher salt concentration

Question 12

How is an electrical gradient involved in cell polarity?

Answer 12

The rhizoid will grow at the negative end

Question 13

What does the fact that rhizoid grows at the negative end and the thalus at the positive end when an electrical gradient is applied?

Answer 13

That development of the fucus involves ion gradients and movements

Question 14

How is calcium involved in establishing cell polarity?

Answer 14

There is ca2+ ion efflux at the thalus end which causes it to be negative which is why it is attracted to the positive end of the electrical gradient. At the rhizoid end there is a localisation of calcium ion channels causing calcium influx and that end of the cell to be positive which means it is attracted to the negative end of the electrical gradient

Question 15

Some zygotes already have asymmetry; why is this?

Answer 15

due to localised cytoplasmic determinants

Question 16

How are localised cytoplasmic determinants involved in determining cell fate?

Answer 16

The distrubutuon of these in different cells causes different cells to become different things

Question 17

What are two good systems for studying localised cytoplasmic determinants?

Answer 17

Amphibians and ascidians (sea squirt)

Question 18

Why is the ascidian (Sea squirt) a good model for cytoplasmic determinant study?

Answer 18

Because it is coloured depending on what cytoplasmic regions are in it and these regions go on to become different tissues so you can see what the cytoplasmic determinants functions are

Question 19

How could you test that it was the cytoplasmic determinants in this region that cause it to turn into the tissue it does?

Answer 19

Transplant these in a different region of the cell to see if that tissue forms there

Question 20

What do local cytoplasmic determinants establish in drosophillia>

Answer 20

The anterior posterior axis

Question 21

At what point in drosophillia development does establishment of the anterior-posterior axis by LCDs occur?

Answer 21

In the oocyte

Question 22

What is isthe dros oocyte surrounded by?

Answer 22

Nurse cells

Question 23

What do nurse cells do?

Answer 23

They synthesised macromolecules (mRNA proteins) and transfer them to the oocyte via cytoplasmic bridges

Question 24

What is a macromolecule that nurse cells transfer to the oocyte in order to establish anterior-posterior axis?

Answer 24

Bicoid mRNA

Question 25

What does the end that bicoid mRNA is localised at become?

Answer 25

The anterior end

Question 26

How can you tell that bicoid is a localised cytoplasmic determinant involved in anterior development?

Answer 26

Because in a bicoid mutant (has no bicoid mRNA) two posterior ends develop

Question 27

How is the bicoid protein localised at the anterior pole?

Answer 27

It is transferred to the oocyte in the mRNA form from the nurse cell where is is transcribed in the anterior pole in the bicoid protein which can then regulate the development of the anterior end

Question 28

What is bicoid an example of ?

Answer 28

A maternal effect gene

Question 29

What is a maternal effect gene?

Answer 29

A gene that is transcribed by the parent/mother cell and it then transferred to the oocyte

Question 30

What are the two maternal effect genes that regulate production of anterior structures?

Answer 30

Bicoid and Hunchback

Question 31

What are the two maternal effect genes that are involved in regulation of the posterior structure prodocution?

Answer 31

Nanos and Caudal

Question 32

What kind of proteins are hunchback, bicoid and caudal?

Answer 32

Transcription factors

Question 33

Where is the bicoid mRNA localised?

Answer 33

The anterior end

Question 34

Where is the nanos mRNA localised?

Answer 34

The posterior end

Question 35

Where are caudal and hunchback mRNA localised?

Answer 35

They are not localised all throughout the structure

Question 36

What causes caudal mRNA to only be transcribed at the posterior end?

Answer 36

Bicoid inhibits it at the anterior end

Question 37

What causes hunchback to only be trancribed at the anterior end?

Answer 37

Nanos inhibits it at the posterior end