Chapter 10 sea urchins

Question 1

Sea urchins undergo _______ cleavage

Answer 1

radial holoblastic cleavage

Question 2

in sea urchins, cell division is _______ and perpendicular to one another in the 1st and 2nd division, and _______ in the 3rd division

Answer 2

meridional
equatorial

Question 3

in sea urchins animal pole cells: _______ division yielding 8 equally sized _______

Answer 3

meridional
mesomeres

Question 4

in sea urchins vegetal pole cells:
unequal _______ division yielding _______ and _______

Answer 4

equitorial
micromeres
macromeres

Question 5

sea urchins:
By the _______ division, the cells become specified and develop cilia on the region outer face of the membrane

Answer 5

10th division

Question 6

Sea urchins:
the ciliated blastula begins to _______ within the fertilization envelop and vegetal pole cells thicken and form the _______

Answer 6

rotate
vegetal plate

Question 7

Sea urchins:
The animal pole cells secrete _______ that dissolves the fertilization envelop

Answer 7

hatching enzyme
- once this occurs it becomes a free-swimming hatched blastula

Question 8

Sea urchin fate maps:
animal half consistently forms _______

Answer 8

ectoderm
- skin and neurons

Question 9

Sea urchin fate maps:
Veg1 cells form _______ and _______

Answer 9

ectoderm and endodermal organs

Question 10

Sea urchin fate maps:
Veg2 cells form several fates (3), what are they?

Answer 10

1) endoderm
2) coelom
3) non-skeletogenic mesenchyme

Question 11

What are 3 examples of what non-skeletogenic mesenchyme turn into?

Answer 11

1) pigment cells
2) immunocytes
3) muscle cells

Question 12

Large micromeres will end up forming _______

Answer 12

skeletogenic mesenchyme

Question 13

Small micromeres have _____ role in development, they end up becoming a part of the _______

Answer 13

no
coelom

Question 14

The large micromeres are _______ specified

Answer 14

autonomously

Question 15

Large micromeres inherit ________ determinants deposited in the vegetal pole of the egg

Answer 15

maternal
- segregated into micromeres in the 4th division
- determines skeletogenic mesenchyme

Question 16

Large micromeres will separate from the _______ and enter the blastocoel, attach to various points on the inside of the wall and differentiate into the larval skeleton

Answer 16

epithelium

Question 17

The large micromeres _______ specify their neighbors

Answer 17

conditionally
- via paracrine and juxtacrine factors

Question 18

Cells above the Large micromeres are conditionally specified to become _______, and will _______ during gastrulation

Answer 18

endoderm
invaginate

Question 19

Skeletogenic mesenchyme cells from the large micromeres are specified by a _______ ciruit

Answer 19

double negative circuit

Question 20

_______, _______, and _______ are inherited maternal cytoplasmic factors (TFs) that are a part of the double negative circuit

Answer 20

disheveled
Otx
β-catenin

Question 21

β-catenin and Otx activate _______, which is a repressor of _______

Answer 21

Pmar1
HesC

Question 22

Repression of _______ allows the transcription of the genes involved in micromere specification
ex) Alx1, Ets1, Tbr, Tel, SoxC

Answer 22

HesC

Question 23

_______ : a single gene activates the transcription of many others

Answer 23

feed-forward regulation

Question 24

Once specified, sea urchin _______ genes are activated by a feed-foward system

Answer 24

skeletal differentiation

Question 25

β-catenin and Otx in micromeres also activate _______ transcription

Answer 25

Blimp1 - they also activate Pmar1 (see above)

Question 26

Blimp1 and β-catenin together activated the _______ gene

Answer 26

Wnt8

Question 27

**Wnt8** is a paracrine/autocrine signal that does what 2 things?

Answer 27

1) stimulates producing cells to produce **more** β-catenin 2) sets up a positive feedback loop ensuring β-catenin production

Question 28

_______, a juxtacrine protein controlled by the double-negative gate, activates the production of _______ protein in adjacent vegetal cells Where is each produced?

Answer 28

delta - produced by large micromere notch - in Veg2

Question 29

Notch activation specifies these adjacent vegetal cells to become _______

Answer 29

Non-skeletogenic mesenchyme

Question 30

Sea urchin gastrulation begins with a _______ blastula of about 1000 cells flattened at one end

Answer 30

single-layered

Question 31

The first step to sea urchin gastrulation is _______ of skeletogenic mesenchyme

Answer 31

ingression

Question 32

ingression: Large micromeres lose their affinity for their _______ and the _______ membrane and ingress into the blastocoel

Answer 32

neighbors hyalin - in turn gain affinity for basal lamina

Question 33

Micromeres _______ their membrane cadherins and other receptors and replace them

Answer 33

endocytose

Question 34

The process of endocytosing cadherins and receptors is controlled by _______

Answer 34

Snail

Question 35

Snail is a protein activated by the _____ transcription factor of the double-negative gate

Answer 35

Alx1

Question 36

Ingressing micromeres acquire a strong affinity for several proteins lining the blastocoel (paracrine factors) such as: (2)

Answer 36

1) VEGF 2) Fibroblast Growth Factor (FGF)

Question 37

Skeletogenic mesenchyme cells accumulate near the sites of VEGF/FGF productinon and fuse into _______ which will form the axis of **Calcium Carbonate Spicules** that form the larval **skeleton**

Answer 37

syncytial cables

Question 38

cells remaining at the vegetal plate after the departure of the skeletogenic mesenchyme flatten and begin to invaginate about 1/4 to 1/2 of the way into the blastocoel. The invaginated region is called the _______

Answer 38

archenteron

Question 39

The opening formed at the vegetal pore as a result of invagination is called the _______

Answer 39

blastopore

Question 40

Cells become specified as they are ingressing into the archenteron: 1) First: non-skeletogenic mesenchyme will become the _______ cell, _______ around the gut 2) deepest archenteron cells become _______ 3) medium depth cells become the _______ 4) last cells to enter become the _______ and _______

Answer 40

1) pigment; musculature 2) foregut 3) midgut 4) hindgut and anus

Question 41

The archenteron then extends dramatically via a process of _______

Answer 41

convergent extension - cells move over one another and flatten archenteron

Question 42

During the 2nd-3rd stages of archenteron invagination, continued cell division at the top of the archenteron form _______ and _______ cells

Answer 42

endodermal secondary mesenchymal

Question 43

Secondary mesenchyme cells at the top send out small projections called _______

Answer 43

filipodia

Question 44

Once filipodia find the correct cells, they are _______ so that the archenteron comes into contact with the **inside** of the **animal pole cells**

Answer 44

PULLED

Question 45

As contact is made between filipodia and animal pole cells, 2nd mesenchyme cells disperse to form _______

Answer 45

internal organs

Question 46

A _______ forms at the point of contact and fuses with the archenteron completing the digestive tube

Answer 46

mouth