Blastula to Gastrula

Question 1

What event occurs following fertilization?

Answer 1

Cleavage

Question 2

Cells formed from the division of zygotic cytoplasm into numerous smaller cells are called?

Answer 2

Blastomeres

Question 3

Mid blastula transition is characterized by what?

Answer 3

Slow-down rate of mitosis and onset of zygotic transcription

Question 4

What is formed at the end of cleavage?

Answer 4

Blastula

Question 5

Does the morphology of blastula stay the same for every species?

Answer 5

No

Question 6

How many cells does human blastodisc have?

Answer 6

70-100 cells

Question 7

Name the organism these varieties of blastula form in
i. Blastula
ii. Blastodisc
iii. Blastocyst

Answer 7

i. Xenopus
ii. Human
iii. Mouse

Question 8

Formation of blastocyst begins at how many days post-fertilization?

Answer 8

5 days

Question 9

Place the events of syncytial blastoderm formation in early embryogenesis of Drosophila in order
a. Nuclei moves to periphery
b. Mid-blastula transition; zygotic transcription and asynchronous divisions; gastrulation begins
c. Cell membranes form to create the cellular blastoderm (single layer of cells around yolky core)

Answer 9

a, c, b

Question 10

Morula is (totipotent/pluripotent) and blastocyst is (totipotent/pluripotent)

Answer 10

Totipotent; pluripotent

Question 11

What is the series of cell movements and migration involving the entire embryo?

Answer 11

Gastrulation

Question 12

What are the three germ layers of gastrulation?

Answer 12

Mesoderm, ectoderm, endoderm

Question 13

Cells that will form the endoderm and mesoderm are brought to the (outside/inside) and ectoderm spread over (inside/outside) surface

Answer 13

Inside; outside

Question 14

Identify the gastrulation cell movement
a. Rows of cells move between one another, creating an array of cells that is longer
b. Cells intercalate in a highly directional manner; embryo elongates
c. A sheet of cells (epithelial sheet) bends inwards
d. An epithelial sheet rolls inwards to form an underlying layer
e. Sheet of cells spread by thinning; movement of cells over another layer of cells
f. Individual cells leave epithelial sheet and become freely migrating mesenchyme

Answer 14

a. Intercalation
b. Convergent extension
c. Invagination
d. Involution
e. Epiboly
f. Ingression

Question 15

Apical constriction is a process in which cell movement of gastrulation?

Answer 15

Involution

Question 16

Xenopus cells involute at which site?

Answer 16

Dorsal blastopore lip

Question 17

What is the mechanism of epithelial-to-mesenchymal transition?

Answer 17

Junctional complexes break down
Basement membrane breaks down
Ingressing cell takes on phenotype of mesenchyme
Cell leaves the epithelial layer of epiblast (ectoderm) and contributes to mesoderm or endoderm

Question 18

Which gastrulation movement in chicks contribute to the formation of the primitive streak?

Answer 18

Ingression

Question 19

Epidermis, neural tissue and placodes are formed from which germ layer?

Answer 19

Ectoderm

Question 20

Epithelial lining of gut, lung, liver and pancreas are formed from which germ layer?

Answer 20

Endoderm

Question 21

Dermis, muscle, bone, kidney and gonads are formed from which germ layer?

Answer 21

Mesoderm

Question 22

Cells in the peripheral and enteric nervous systems, craniofacial bones and cartilage are formed from a fourth germ layer. What is it called?

Answer 22

Neural crest cells

Question 23

What is a group of cells that are capable of organizing neighboring cells?

Answer 23

Organizer

Question 24

An organizer can induce ectopic cell fates in host tissue following ___________ transplantation

Answer 24

Heterotopic

Question 25

What is the Mangold Spemann experiment?

Answer 25

Grafting the cells from the dorsal blastopore lip and transplanting them to a different side of the embryo

Question 26

What did Mangold and Spemann find in their experiment?

Answer 26

Transplantation of dorsal blastopore lip generates a second axis that is patterned The neighboring cells of the transplanted cells were induced to form another invagination

Question 27

What can transplantation of Hensen's node induce?

Answer 27

A regionally structured (A-P) neural axis

Question 28

On the ventral side of the embryo, which molecule downregulates the level of nodal-related genes to originate the ventral mesoderm?

Answer 28

VegT, Vg1

Question 29

On the dorsal side of the embryo, which molecule upregulates the level of nodal-related genes to originate the organizer?

Answer 29

Beta-catenin

Question 30

Bmp4 and Bmp7 are molecular signals required for patterning the ___________ centre

Answer 30

Ventral

Question 31

Chordin, Noggin, Follistatin and Dickkopf-1 are required for the ____________

Answer 31

Organizer

Question 32

Bmp4 and Bmp7 are (agonists/antagonists) and Chordin and Noggin are (agonists/antagonists)

Answer 32

Agonists; antagonists

Question 33

Frzb-1, DicKkopf-1 and Crescent inhibit _________, _________ inhibits Xnrs, Xwnt-8 and BMPs and Chordin, Noggin and Follistatin inhibit _________

Answer 33

Wnts; Cerberus; BMPs

Question 34

What defines a direction or orientation?

Answer 34

An axis

Question 35

What are the three major axes in the early embryo?

Answer 35

Anterior-posterior, dorsal-ventral, left-right

Question 36

What is the axis present in older embryos?

Answer 36

Proximal-distal

Question 37

Unfertilized egg is usually radially ___________

Answer 37

Symmetrical

Question 38

Initial divisions after fertilization can generate functionally _______________ daughter cells

Answer 38

Equivalent

Question 39

How do the cells become different?

Answer 39

Asymmetric cell division and asymmetric patterning through inductive signals

Question 40

In mammals, where does the dorsal axis form?

Answer 40

Inner cell mass cells in contact with the trophoblast

Question 41

In chick formation, the dorsal axis is the side facing (yolk/albumen) and it is pH dependent

Answer 41

Albumen

Question 42

In Drosophila, the dorsal axis is found where?

Answer 42

Syncytial blastoderm

Question 43

The dorsal protein in Drosophila is (present/absent) in all nuclei if the embryo becomes dorsalized and (present/absent) in all nuclei if the embryo becomes ventralized

Answer 43

Absent; present

Question 44

Which ligand controls the entry of Dorsal protein into the nucleus?

Answer 44

Spatzle binding to Toll receptor

Question 45

When does DV axis patterning start in mouse, chick, Drosophila and Xenopus?

Answer 45

Mouse: blastula Chick and Drosophila: blastoderm Xenopus: Fertilization