Multicellularity 1 Flashcards
1
Q
How many times has multicellularity evolved?
A
- 6 times in plants
- 3 times in fungi
- 1 time in animals (metazoa)
2
Q
What is the closest single celled relative to animals?
A
Choanoflagellates
3
Q
Explain the structure of choanoflaggelates
A
- flagella
- collar
4
Q
What do choanoflaggelates eat?
A
Bacteria
5
Q
What is the presence of actin and tubular in choanoflagellates?
A
- actin - the colar
- tubulin - the flagella
6
Q
What is the animal that choanoflaggelates relate to?
A
sponges
7
Q
What is a choanocyte?
A
- cell type of the sponge
- has a flagellum and collar
8
Q
What are 2 cell types that sponges don’t have?
A
- nerves
- muscle
9
Q
What are the 2 types of tyrosine kinases?
A
- receptor tyrosine kinases (RTK)
- cytoplasmic tyrosine kinases (CTK)
10
Q
Explain tyrosine kinases in choanoflagellates and sponges / animals
A
- cytoplasmic ones found in the common ancestor to choanoflagellates and animals
- receptor ones found only in choanoflagellates and animals, not in choanoglagellates precursor
11
Q
Explain cadherins in choanoflagellates
A
- they are present (23 of them)
- contained SH2, IgG and Hh domains which animal cadherins don’t normally have
-they don’t have the section that would bind cadherin to actin - most common in the collar
- thinking they evolved not for cell-cell adhesion but to bind bacteria for food
12
Q
explain the interactions of Src and Csk
A
- Csk phosphorylates tyrosine in the tail of Sir
- will fold only SH2 domain
- shuts down Src
- Csk is a negative regulator
13
Q
explain the interactions of Src and Csk in chanoflaggelates
A
- negative inhibition doesn’t happen, but phosphorylation does
