Coding 13 Flashcards
Where does the egg in a chick undergo its first cleavage?
While it is in the hen
Where is the chick fertilized before the albumin and the shell are secreted to cover it?
The oviduct
What is the blastodisc?
A small disc of yolk free cytoplasm that sits on top of a large mass of yolky cytoplasm
When does MZT happen?
128 cell stage
In chicks what are the 3 steps of gastrulation?
- Formation of the lower hypoblast and the upper epiblast
- The epiblast makes the primary body structure, head, and neck
- Secondary body formation from the lower abdomen and tail
What is the koller’s sickle?
The posterior end of the area pellucida where the cells thicken and make the anterior-posterior region
What is the hypoblast?
The cells that lead the gut formation and the yolk sac
What part of the egg undergoes cleavage?
The blastodisc in the animal pole
What is the epiblast?
Cells that make the germ layer and the extraembryonic membrane
What is the posterior marginal zone?
A beltlike region between the area opaca and the koller’s sickle
How is the blastocoel cavity made?
By the epiblast and the hypoblast joining at the PMZ
How is the primitive streak made?
The clockwise and counterclockwise motion of thousands of epiblast cells
What is the primitive groove?
Cells that converge at the primitive streak and form a depression
What is the hensen’s node?
The anterior end of the primitive streak
How does the primitive streak play a role in body axes?
When cells ingress through the streak somite formation occurs
What is the PMZ analogous to?
The nieukwoop centre
How is PMZ similar to NC?
It secretes Vg1 (nodal protein) and it is localized to the side due to BMP4 inhibition and nodal proteins are needed for primitive streak formation
What happens once the primitive streak has completed its formation?
It secretes cerebrus to repress its own nodal proteins and formation
When is germ layer identity established?
Before gastrulation
What do the first cells that ingress through the hensen’s node make?
Pharyngeal endoderm
What do the second cells that ingress through the hensen’s node make?
Presumptive foregut endodermal cells
What do the third cells that ingress through the hensen’s node make?
Choramesoderm cells
What is the mammalian oocyte wrapped in?
Cumulus cells
What takes the oocyte from the ovary to the oviduct?
Fimbirae
Where does fertilization occur?
Near the ovary in the ampulla
What does the first cleavage depend on?
The location of sperm entry
What is compaction?
When adhering proteins such as E-cadherins are expressed and the blatomeres cluster into a ball
When does compaction occur?
In the third cleavage
At the 16-cell stage there is a division into internal and external cells that form?
The internal makes the ICM
The external makes the trophoblast
What are the inner cell mass cells?
Pluripotent embryonic cells
What are the trophoblast cells?
Totipotent cells that can make any embyronic structure
What do trophoblast cells do in humans?
Make hormones by embedding in the uterus to prevent fetus rejection
Do mammals receive nutrients from their yolk sac?
No from the mother through the placenta
How is the placenta made?
When the trophoblast cells bind to the mesoderm to make a capillary-rich chorion structure
The ICM makes the epiblast which makes what?
Amnion, allantois and the embyro
The ICM makes the primitve endoderm which makes what?
Yolk sac
What makes up the bilaminar germ disc?
The primitive endoderm and the epiblast
What makes the amnion with amniotic fluid?
Epiblast cells
How does the epiblast cells make the endoderm and the mesoderm?
Through EMT
What is the node?
A thickened bulb of cells at the anterior of the primitive streak that makes the mesoderm and the notochord
Between the trophoblast and the epiblast what structure is initiated?
The primitive streak
What is the NC equivalent in zebrafish?
Yolk syncitial layer
Where does the B-catenin build up?
Yolk synchitial layer
What is the zebrafish organizer?
Embryonic shield
What does the nuclear B catenin accumulation lead to?
The activation of BMP and WNT inhibitors
What is chordino?
BMP inhibitor activated by B catenin -> Nodal
What is goosecoid?
BMP and WNT inhibitor
What is noggin?
BMP inhibitor
What is dickkopf?
Wnt inhibitor
What is siamois?
A protein produced in the dorsal lip (and not secreted) that turn on goosecoid, which help specify dorsal mesoderm development VegT and Vg1 turn on Xnr, which diffuses up and induces mesoderm
What is the avian organizer?
Hensen’s node
What is the purpose of floped, filia, and TLE6 what happens if they are preturbed?
Asymmetric cell division during cleavage
Where are the cilia relative to the node?
The ventral surface of the node
What is situs inversus?
Reverse left-right asymmetry
What is kartagener syndrome?
- Situs inversus
- Male sterility
- Constant bronchitis
What is the role of nodal in the left-right asymmetry generation?
Nodal is expressed in the left and it flows
- It inhibits WNT and BMP
- It activates Ptx2
- The morphogen gradient leads to the activation of the immotile cilia at the end
- Cellular responses occur due to the gradient
What is a homeobox?
It is is a gene
What is a homeodomain?
It is a DNA binding domain for a transcription factor
What do hox genes determine?
The anterior-posterior region
Do paralogs have an identical amino acid sequence?
No they are similar
What is colinearity?
When the genes expressed correspond to the order of the segments
What is posterior prevalence?
When the posterior function of the posterior Hox genes overwhelm the anterior hox genes
What do the most anterior hox genes make?
The hindbrain, base of the skull, occipital, and the ears
How do you mis-express a hox gene?
Conducting a transplant and add a transgene containing the gene of interest
What is the difference between mouse and chicken segments?
The chicken segments are shifted 7 somites over
What does it mean by redundant genes?
You do not need all of the genes in order to see the phenotype what you need is only one paralog
What is misexpression?
It is not that it does not form rather it is converted into something else
What is a Hox LOF do?
Anterior forms in the posterior
What is a Hox GOF do?
Posterior regions form in the anterior
If you mutate the Hox1 family what happens?
Facial abnormalities
How does the blastocoel cavity form?
The epiblast and hypoblast join at the marginal zone
What is equivalent to the posterior marginal zone?
The nieukwoop center
For the cells that ingress through Hensen’s node first what does that make?
Pharyngeal endoderm
For the cells that ingress through Hensen’s node second what does that make?
The forebrain
What causes left-right asymmetry?
The flow of the nodal from right to left because of the motile cilia
What makes the neural plate?
Ectoderm
What makes the neural crest cells?
Ectoderm
