Blastula to Gastrula Flashcards
What event occurs following fertilization?
Cleavage
Cells formed from the division of zygotic cytoplasm into numerous smaller cells are called?
Blastomeres
Mid blastula transition is characterized by what?
Slow-down rate of mitosis and onset of zygotic transcription
What is formed at the end of cleavage?
Blastula
Does the morphology of blastula stay the same for every species?
No
How many cells does human blastodisc have?
70-100 cells
Name the organism these varieties of blastula form in
i. Blastula
ii. Blastodisc
iii. Blastocyst
i. Xenopus
ii. Human
iii. Mouse
Formation of blastocyst begins at how many days post-fertilization?
5 days
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)
a, c, b
Morula is (totipotent/pluripotent) and blastocyst is (totipotent/pluripotent)
Totipotent; pluripotent
What is the series of cell movements and migration involving the entire embryo?
Gastrulation
What are the three germ layers of gastrulation?
Mesoderm, ectoderm, endoderm
Cells that will form the endoderm and mesoderm are brought to the (outside/inside) and ectoderm spread over (inside/outside) surface
Inside; outside
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
a. Intercalation
b. Convergent extension
c. Invagination
d. Involution
e. Epiboly
f. Ingression
Apical constriction is a process in which cell movement of gastrulation?
Involution
Xenopus cells involute at which site?
Dorsal blastopore lip
What is the mechanism of epithelial-to-mesenchymal transition?
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
Which gastrulation movement in chicks contribute to the formation of the primitive streak?
Ingression
Epidermis, neural tissue and placodes are formed from which germ layer?
Ectoderm
Epithelial lining of gut, lung, liver and pancreas are formed from which germ layer?
Endoderm
Dermis, muscle, bone, kidney and gonads are formed from which germ layer?
Mesoderm
Cells in the peripheral and enteric nervous systems, craniofacial bones and cartilage are formed from a fourth germ layer. What is it called?
Neural crest cells
What is a group of cells that are capable of organizing neighboring cells?
Organizer
An organizer can induce ectopic cell fates in host tissue following ___________ transplantation
Heterotopic
What is the Mangold Spemann experiment?
Grafting the cells from the dorsal blastopore lip and transplanting them to a different side of the embryo
What did Mangold and Spemann find in their experiment?
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
What can transplantation of Hensen’s node induce?
A regionally structured (A-P) neural axis
On the ventral side of the embryo, which molecule downregulates the level of nodal-related genes to originate the ventral mesoderm?
VegT, Vg1
On the dorsal side of the embryo, which molecule upregulates the level of nodal-related genes to originate the organizer?
Beta-catenin
Bmp4 and Bmp7 are molecular signals required for patterning the ___________ centre
Ventral
Chordin, Noggin, Follistatin and Dickkopf-1 are required for the ____________
Organizer
Bmp4 and Bmp7 are (agonists/antagonists) and Chordin and Noggin are (agonists/antagonists)
Agonists; antagonists
Frzb-1, DicKkopf-1 and Crescent inhibit _________, _________ inhibits Xnrs, Xwnt-8 and BMPs and Chordin, Noggin and Follistatin inhibit _________
Wnts; Cerberus; BMPs
What defines a direction or orientation?
An axis
What are the three major axes in the early embryo?
Anterior-posterior, dorsal-ventral, left-right
What is the axis present in older embryos?
Proximal-distal
Unfertilized egg is usually radially ___________
Symmetrical
Initial divisions after fertilization can generate functionally _______________ daughter cells
Equivalent
How do the cells become different?
Asymmetric cell division and asymmetric patterning through inductive signals
In mammals, where does the dorsal axis form?
Inner cell mass cells in contact with the trophoblast
In chick formation, the dorsal axis is the side facing (yolk/albumen) and it is pH dependent
Albumen
In Drosophila, the dorsal axis is found where?
Syncytial blastoderm
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
Absent; present
Which ligand controls the entry of Dorsal protein into the nucleus?
Spatzle binding to Toll receptor
When does DV axis patterning start in mouse, chick, Drosophila and Xenopus?
Mouse: blastula
Chick and Drosophila: blastoderm
Xenopus: Fertilization
