L8 - Polarity 1

Question 1

What is cell polarity?

Answer 1

Cell polarity – organisation of proteins inside, and at surface of cells

Question 2

Why is budding yeast used to study cell polarity? (3)

Answer 2

-Yeast undergoes morphological changes in response to both internal and external signals
-It’s a very easy model to use as it has less complexity
-It is genetically tractable as we know what most genes do

Question 3

What are the 4 functional requirements in developing cell polarity (in eukaryotes)? (4)
and what do they mean (4)

Answer 3

-Marking the site (to differentiate one part of itself to another part)

-Decoding the site (cell needs to know location of event/signals/proteins to make site change)

-Establishing the site (where key proteins come to site and start organising cytoskeleton to send things to different areas)

-Maintaining the site (feedback loop to make sure things go back to where they need to be recognised)

Question 4

What is cell polarity critical for? (3)

Answer 4

1) Asymmetric cell division - including cell fate decisions
2) Epithelial cells – to make an effective barrier
3) Cell migration eg in development

Question 5

Which budding pattern is used for budding yeast to “mark the site”?

Answer 5

-Haploid have AXIAL pattern (each bud come from where previous bud was)

Question 6

Which budding pattern is used when there is a mutation in genes for yeast axial budding?

Answer 6

-Diploid so bipolar pattern, move cells away to explore wider environment for nutrition

Question 7

Which genes are required for:
Yeast axial budding pattern -
Yeast bipolar budding pattern -
Both axial and bipolar -
Establishing the site -

Answer 7

Yeast axial budding pattern - BUD10, BUD3, BUD4
Yeast bipolar budding pattern - BUD8,BUD9,RAX2
Both axial and bipolar - BUD1, BUD2, BUD5
Establishing the site - Cdc42(main), Cdc43,Cdc24

Question 8

What is mating in budding yeast signalled by?
what are they detected by?

Answer 8

-Pheromones
-GPCRs

Question 9

Which cells and factors are involved in mating in budding yeast?

Answer 9

MATa cells secrete a-factor and MATa cells secrete a-factor. MATa cells have a receptor on their cell surface (Ste2) that can bind to a-factor and MATa cells have a receptor (Ste3) that can bind to a-factor

Question 10

What is the difference in cell cycle between mother and daughter yeast cell? (2)

Answer 10

-Daughter cell different from mother as can inherit different MRNAs

-Cell cycle in daughter cell starts and different time and can undergo mating type switching unlike mother