Amphibians II

Question 1

What is purpose of gray crescent?

Answer 1

It has dorsalizing capability

Question 2

What happens after cortical rotation?

Answer 2

Cleavage

Question 3

What is important about the first three cleavages?

Answer 3

They are perpendicular to each other. Third cleavage is horizontal.

Question 4

Is frog embryo cleavage complete or incomplete?

Answer 4

complete (holoblastic)

Question 5

How is yolk distributed?

Answer 5

Mesolecithal, moderately distributed on the vegetal pole side

Question 6

What do they mean when they say “displaced cleavage”?

Answer 6

there is more cleavage on the animal hemisphere, resulting in smaller blastomeres on that side

Question 7

After many cleavages, what does the embryo ultimately become?

Answer 7

A blastula or a hollow ball of cells

Question 8

What is the blastocoel?

Answer 8

a fluid filled cavity in the blastula?

Question 9

What does a blastula at the mid-blastula stage go through?

Answer 9

Mid-blastula transition

Question 10

What happens during mid-blastula transition?

Answer 10

1. the blastula will express zygotic genes (its own genes)
2. cells will become motile
3. cell fates are specified

Question 11

What is specification?

Answer 11

cells are capable of forming by themselves (autonomously) when in isolation in a neutral environment

Question 12

What does a fate map show?

Answer 12

shows what the specific regions in the embryo will differentiate into during development

Question 13

What is differentiation?

Answer 13

the process by which a cell becomes specialized into one particular cell type

Question 14

Does differentiation potential increase or decrease over time?

Answer 14

decrease

Question 15

What is explantation?

Answer 15

When you explant a cell and move it in a petri dish

Question 16

What happens if you explant a cell before vs after mid-blastula translation?

Answer 16

Early blastula: the cell will not become anything
Late blastula: cell will follow its original fate

Question 17

What is transplantation?

Answer 17

Moving cell to another region

Question 18

What happens if you transplant a cell before vs after mid-blastula translation?

Answer 18

Both cells will assume the fate of the new surrounding region

Question 19

What is competence?

Answer 19

the ability of cells to become different kinds of cells upon the influence of appropriate neighbors or environment (inductive signals)

Question 20

What happens to final/late blastula?

Answer 20

It undergoes gastrulation

Question 21

What is involution?

Answer 21

textbook: inward movement of an expanding outer layer so that it spreads over the internal surface of the remaining external cells

Question 22

What is epiboly?

Answer 22

textbook: movement of epithelial sheets (usually ectodermal cells) spreading as a unit to enclose deeper layers of the embryo
summary: surface cells expand

Question 23

What is relative position of gray crescent to sperm entry point?

Answer 23

they are opposites

Question 24

What is IMZ?

Answer 24

involuting marginal zone;

Question 25

What is NIMZ?

Answer 25

non-involuting marginal zone;

Question 26

What happens during the first stage of gastulation?

Answer 26

the bottle cells invaginate into the embryo and lead the cells in the dimple on the IMZ to follow

Question 27

What is the second stage of gastrulation?

Answer 27

IMZ cells on the dorsal side aggregate and extend in length from the bottom to the top

Question 28

What was the most famous experiment by Spemann?

Answer 28

Spemann Organizer - They took the late blastula of a newt and transplanted the dorsal lip of blastopore to another recipient (so it had two). They saw that the recipient underwent two invaginations and it ended up having two heads.

Question 29

What is archenteron?

Answer 29

primitive gut