Midterm 2.0 Flashcards
Unc 40 - what is it?
Unc 40 mutant
A receptor that mediates attraction to netrin
In an Unc 40 mutant, axons that go towards the midline don’t, but axons that usually go away from the midline are still okay
Netrin (Unc 6) - what is it and what does it do
Unc 6 mutant ?
A secreted protein that’s produced/ formed at the vml
Acts as both a repellant and attractant
In an Unc 6 mutant, neurons didn’t send axons toward or away from the vml
Unc 5 - what is it
Unc 5 mutant
A receptor that mediates repulsion to Netrin
In an Unc 5 mutant, axons that normally go away don’t, but axons that normally go toward the vml still do
Slit - what is it
Slit mutant
A repellant produced at the vml
All of the axons would pile up at the vml
Robo 1, 2, 3 - what are they? Which is the most important/strongest?
Robo 1 mutant?
Robo 1,2,3 mutant?
Each of them are receptors for slit
Robo 1 is the most important/ strongest. It causes a very significant effect/ phenotype
In a Robo 1 mutant, the result is a “roundabout phenotype”, because Robo 2 and 3 are still active
Robo 1,2,3 mutant - all axons are attracted to the vml, but just get stuck there; all u get is something that looks like a slit. Same as slit mutant
Comm - what does it d?
Comm- mutant?
It downregulates Robo receptors in axons before they cross the vml. It prevents the Robo receptors from reaching the surface of the axons
In a comm- mutant, there is no formation of commisures due to inability to downregulate Robo receptors
What happens in a slit-, comm- mutant?
Same as slit- mutant; doesn’t matter if comm is absent, cuz Slit is absent in the first place
What happens when Comm is over expressed?
Downregulate Robo receptors; axons would never be able to detect slit because there’s too much Comm preventing the Robo receptors from reaching the surface.
Same as a slit- mutant
How are axons able to cross the vml if the Slit repellant is present?
The Robo receptors are not put on the surface yet because Comm prohibits it, and the axons are able to travel toward the vml.
Once the axon gets to the vml, the effect of Comm is lost, and Robo receptors appear for the first time on axon surface, which leads to repulsion by Slit.
The axons now move away from the vml.
What is a fasciclin; how is it present in SNb and SNa?
A homophilic adhesion molecule; on two different cells, it likes to bind to each other; present in SNb and SNa axon tracks as fasII
What is the basis of SNb and SNa
SNb and SNa travel upward together, but then SNb separates from SNa at an exit point; SNb and SNa then get into contact with different muscles and eventually arrive at their final destinations
