Vertebrate Development IV Flashcards
T or F: relatively little is known about the early stages in chick development as they take place before the egg is laid
TRUE
The antero-posterior polarity of the chick blastoderm is related to the ___1.___
- primitive streak
Cleavage begins after ___1.___ while the egg is still in the hen’s ___2.___
- fertilization
2. oviduct
At the time of laying, the embryo is a ___1.___ cellular blastoderm lying on top of a ___2.___ , which is surrounded by the egg white and shell
- disc-shaped
2. massive yolk
The ___1.___ indicates the direction of the antero-posterior axis of the embryo, with the node called ___2.___ node forming at its ___3.___ end
- primitive streak
- Hensen’s
- anterior
T or F: it is not clear whether any maternal factors are inherited asymmetrically during cleavage and determine the embryonic axis
TRUE
The ___1.___ axis seems to be specified later, as a result of ___2.___ forces as the egg passes through the hen’s ___3.___ and ___4.___
- antero-posterior
- rotational
- oviduct
- uterus
KEY POINT: ___1.___ gene activation occurs at late ___2.___ stages!
- zygotic
2. cleavage
T or F: the antero-posterior axis is irreversibly determined by rotational forces of the egg
FALSE (it is not irreversibly)
T or F: Even at the stage when the blastoderm contains several tens of thousands of cells, it can be cut into many fragments each of which will develop a complete embryonic axis
TRUE
The ___1.___ zone can be thought of as an ___2.___ center analogous in some ways with the ___3.___ in Xenopus
- posterior marginal
- organizing
- Nieuwkoop center
T or F: the mammalian egg differs considerably from the eggs of either the frog or the chick
TRUE
T or F: the early cleavage divisions in mouse embryos follow a well-ordered pattern
FALSE (they do NOT follow a well-ordered pattern aka regulative development)
By the ___1.___ cell stage, the morula has developed into a ___2.___
- 32
2. blastocyst
The development of cells as either ___1.___ or ___2.___ in early mouse embryos depends on their position in the cleaving embryo
- inner cell mass
2. trophectoderm
Determination of their fate occurs after the ___1.___, and during earlier stages all the cells seem to be equivalent in their ability to give rise to either tissue
- 32-cell stage
The cells of the ___1.___ are ___2.___ and can give rise to all cell types of the embryo including ___3.___ , in vitro
- epiblast
- pluripotent
- germ cells
The embryonic-abembryonic axis corresponds in a geometric sense to the ___1.___ axis of the future ___2.___ , but not in terms of cell fate
- dorso-ventral
2. epiblast
The formation of the ___1.___ appears at the ___2.___ end of the antero-posterior axis in the epiblast
- primitive streak
2. posterior
The ___1.___ of the epiblast cup corresponds to the ___2.___ side of the future embryo and outer side to the future ___3.___ side
- anterior
- dorsal
- ventral
T or F: mesoderm induction and patterning in the chick and mouse occurs during primitive streak formation, with different regions of the streak giving rise to different mesodermal tissues along the dorso-ventral axis
TRUE
___1.___ family members can act as mesoderm-inducing and/or ___2.___-patterning signals
- TGF-beta
2. mesoderm
The node that develops at the ___1.___ end of the streak in ___2.___ and mouse embryos is equivalent to the ___3.___ in Xenopus
- anterior
- chick
- Spemann
T or F: after extending to its full length, the primitive streak begins to regress anteriorly
FALSE (posteriorly instead of anteriorly)
As it does so, the ___1.___ (head process) is formed by ___2.___ cells that emerged from the ___3.___ tip of the streak and moves ___4.___
- notochord
- mesodermal
- anterior
- forward
The ___1.___ and ___2.___ overlying the head process form in the epiblast ___3.___ to the furthest extent of the ___4.___
- head fold
- neural plate
- anterior
- primitive streak
The edges of the ___1.___ begin to rise up to form the ___2.___ and the first ___3.___ appears
- neural plate
- neural folds
- somite
___1.___ induction in chick and mouse is initiated by ___2.___ signaling with inhibition of ___3.___ signaling being required in a later step
- Neural
- FGF
- BMP
___1.___ are formed in a well-defined order along the antero-posterior axis
- Somites
Identity of somites along the ___1.___ axis is specified by ___2.___ gene expression
- antero-posterior
2. Hox
Deletion or overexpression of ___1.___ gene causes changes in ___2.___ patterning
- Hox
2. axial
The fate of somite cells is determined by signals from the ___1.___
- adjacent tissues
Which internal organs are asymmetric (left-right asymmetry)?
Heart and liver
T or F: left-right asymmetry involves an initial symmetry-breaking event leading to asymmetric gene expression on the left and right sides of the embryo
TRUE
The activity of proton-potassium pump in ___1.___ node is reduced on the left side of the node, leading to a membrane-potential difference across the node and increased release of ___2.___ into the extracellular space on the ___3.___ side of the node
- Hensen’s
- calcium
- left
This leads to a greater activation of ___1.___ signaling on the ___2.___ side of the node which in turn activates expression of the gene ____3.___ in cells on the left side of the node
- Notch
- left
- Nodal
___1.___ signaling together with ___2.___ then switches on Nodal expression on the ___3.___ side, which leads to expression of the transcription factor ___4.___
- Nodal
- Sonic hedgehog (Shh)
- left
- Pitx2
