Cleavage

Question 1

What are a few things that Cleavage accomplishes?

Answer 1

Multicellularity, regionalization, cell-cell interaction and movement, partitioning of localized determinants

Question 2

What is different between the somatic cell cycle, and the embryonic cell division cycle?

Answer 2

There are no gap phases [g1 and g2] in the embryonic cleavage cycle

Question 3

Describe the cleavage division cycle as it pertains to cyclin

Answer 3

Cyclins are synthesized, attached to cdc2 for MPF in the M phase, then degraded in the S phase. This repeats

Question 4

Reductive Cleavage

Answer 4

Each successive cleavage does not really alter total volume of the blastula

Question 5

What is the contractile ring mostly made of?

Answer 5

Actin

Question 6

What is the role of astral microtubules during cleavage?

Answer 6

They align the cleavage furrow and spindle mid zone for the contractile ring

Question 7

What precedes actin polymerization at the contractile ring?

Answer 7

The protein Rho

Question 8

What happens if you block Rho?

Answer 8

There will be multiple nuclei, but no cleavage.

Question 9

How can you block Rho?

Answer 9

With C3 transferase

Question 10

What is the major challenge to increasing the surface area/volume ratio?

Answer 10

You need more membrane

Question 11

Where is new membrane inserted?

Answer 11

At the furrow

Question 12

Isolecithal

Answer 12

uniform, not a lot of yolk

Question 13

Mesolecithal

Answer 13

moderate, slightly more yolk on one end

Question 14

Telolecithal

Answer 14

Lots of yolk, usually at one end

Question 15

Centrolecithal

Answer 15

yolk in the middle

Question 16

Holoblastic Cleavage

Answer 16

complete cleavage

Question 17

Mesoblastic Cleavage

Answer 17

incomplete cleavage

Question 18

What are the main orientations of cleavage?

Answer 18

Radial, spiral, bilateral, rotational, discoidal

Question 19

Cleavage[description,examples]: Holoblastic,Isolecithal, Radial

Answer 19

Echinoderms, amphioxus

Question 20

Cleavage[description,examples]:Holoblastic,Isolecithal,Spiral

Answer 20

Annelids, mollusks, flatworms

Question 21

Cleavage[description,examples]:Holoblastic,Isolecithal,Bilateral

Answer 21

Tunicates

Question 22

Cleavage[description,examples]:Holoblastic,Isolecithal,Rotational

Answer 22

Mammals,nematodes

Question 23

Cleavage[description,examples]:Holoblastic,Mesolecithal,Radial

Answer 23

Amphibians

Question 24

Cleavage[description,examples]:Mesoblastic,Telolecithal,Bilateral

Answer 24

Cephalopods,molluscs

Question 25

Cleavage[description,examples]:Mesoblastic,Telolecithal,Discoidal

Answer 25

fish,reptiles,birds

Question 26

Cleavage[description,examples]:Mesoblastic,Centrolecithal,

Answer 26

Most insects

Question 27

Protostome

Answer 27

Mouth first

Question 28

Deuterostome

Answer 28

Mouth second

Question 29

Cleavage orientation is determined by:

Answer 29

spindle positioning

Question 30

If cells contain less yolk, they tend to be

Answer 30

smaller, and toward the animal hemisphere

Question 31

Where does the blastocoel tend to form?

Answer 31

At the place with the less yolky cells

Question 32

How does the blastocoel create a different ionic content?

Answer 32

Tight Junctions seal off the coel

Question 33

What is a blastoderm?

Answer 33

In mesoblastic chick eggs for example, the cell sheet on top of the yolk

Question 34

Cleavage leads to ___ partitioning

Answer 34

cytoplasmic