Multicellularity

Question 1

What is multicellularity?

Answer 1

organism consisting of more than one cell

Question 2

Rank most to least how many times plants, fungi and animals evolved multicellularity

Answer 2

plants = 6
fungi = 3
animal/metazoa = 1

Question 3

Is fungi more related to plants or animals

Answer 3

animals

Question 4

What is the closest living relative to metazoan that is single cellular organism?

Answer 4

choanoflagellates

Question 5

Describe the structure of choanoflaggelates and what is used for double antibody immunofluorescence?

Answer 5

flagella (tubular) and collar (actin)

Question 5

What is a choanoflagellate?

Answer 5

Bacteria-eating eukaryote

Question 6

What do they lose when they form colonies?

Answer 6

collar and flagella

Question 7

What animal is most related to choanoflagellates?

Answer 7

sponges (choanocytes)

Question 8

Serine, threonine and tyrosine can be ___

Answer 8

phosphorylated

Question 9

What is receptor tyrosine kinase?

Answer 9

proteins that span cell membrane and binds to ligands cauding cross phosphoryla;tion of eachother and downstream enzymes

Question 10

What is cytoplasmic tyrosine kinase?

Answer 10

dont bind ligands and are inside cells not on membranes which phosphorylates tyrosine residue

Question 11

What is found in choanoflagellates? receptor or cytoplasmic tyrosine kinase?

Answer 11

receptor

Question 12

Animals and choanoflagellates significantly increase number of ______ in their genomes

Answer 12

receptor tyrosine kinase

Question 13

Single celled eukaryotes have lots of ____ but not ____

Answer 13

cytoplasmic TK, receptor TK

Question 14

Describe Src activation in choanoflagellates

Answer 14

Src is active = kinase autophosphorylates itself
CSK phosphorylates tyrosine in the tail and it folds back and shuts down src ( acts as a negative regulator)

Question 15

What about src activation in animals?

Answer 15

• regulation of negative inhibition didn’t happen csk does phosphorylate but doesn’t lead to inhibition

Question 16

Are cadherins homolytic or heterolytic

Answer 16

homolytic

Question 17

Why did choanoflagellate (single celled) have so many cadherin genes?

Answer 17

a way to bind to bacteria so it first evolved not for cell adhesion but for catching their food (bacteria)

Question 18

Explain what happens in absence of WNT

Answer 18

• frizzled is the receptor, wnt is unbound
• GSK3B phosphorylation casuses B catenin to be degraded
• everything is off (TCF and responsive genes are turned off)

Question 19

Explain what happens in presence of WNT

Answer 19

• when Wnt binds to frizzled
• pulls GSK3B to receptor and it can not phosphorylate b - catenin
• it accumulates, goes to nucleus and binds TCF

Question 20

What is the result of Wnt responsive cell?

Answer 20

cell shape changes and cytoskeletal changes

Question 21

Does choanoflagellates have Wnt?

Answer 21

No

Question 22

Wnt helps establish axis which give organisms….

Answer 22

symmetry

Question 23

Wnt establish the primary ______ axis of all animals. mainly expressed at ___ end

Answer 23

anterior posterior, tail/posterior

Question 24

What is a flask cell?

Answer 24

precursor of nerves in sponges