Question 1

Mosaic analysis studies have demonstrated that:
A) The product of the Boss gene is required in the future R7 cell to determine R7 cell fate.
B) The product of the Sevenless gene is required in the future R7 cell to determine R7 cell fate.
C) the product of the Sevenless gene is required in the R8 cell to determine R7 cell fate.
D) the product of the Sevenless gene acts cell nonautonomously to determine R7 cell fate.
E) All of the above

Accepted Answer

The product of the Sevenless gene acts cell autonomously in the future R7 cell to receive a signal (Boss) from the R8 cell and determine R7 cell fate.

Question 2

Which of the following general principles can be gleaned from developmental studies of the visual system in vertebrates?
A) Connection specificity that distinguishes discrete cell types is more likely to be determined by molecular cues.
B) Connection specificity that chooses between similar cells tends to involve neuronal activity and competition.
C) Initial targeting by neuronal processes tends to be activity-independent.
D) Refinement of neuronal processes tends to be activity-dependent.
E) All of the above

Accepted Answer

These are the main principles derived from genetic studies, visual input deprivation, and activity manipulation.

Question 3

The signal from R7 that induces Rh5 expression in R8 is as yet unknown. What ommatidial phenotypes would be expected of a loss-of-function mutant for the gene encoding this signal?
A) All R7 cells would express Rh3.
B) All R7 cells would express Rh4.
C) All R8 cells would express Rh5.
D) All R8 cells would express Rh6.
E) Both b and d

Accepted Answer

Loss of the signal would exhibit the same phenotype the loss of R7 cells, resulting in all R8 cells expressing Rh6. However, this should have no effect on the stochastic distribution of Rh3 vs. Rh4 in R7 cells.

Question 4

Both ephrins and cholinergic retinal waves appear to be necessary for normal formation of retinotopic maps in the:
A) superior colliculus.
B) LGN.
C) primary visual cortex.
D) a and b
E) a, b, and c

Accepted Answer

Triple knockout mice lacking ephrin-A2, ephrin-A5, and the F1F1F1S1F1F1F102 subunit of the nicotinic acetylcholinergic receptor exhibit much more severe defects in the superior colliculus and primary visual cortex than the ephrin double knockout mice, indicating that cholinergic retinal waves play a key role in refining the retinotopic maps in these structures. Ephrin expression patterns and experimental manipulation of cholinergic signaling imply that the same is true of the LGN.

Question 5

Which of the following are required for retinal lamina-specific dendritic targeting by RGCs?
A) Neurotransmission from bipolar cells
B) Homophilic cell adhesion proteins
C) Semaphorins and their receptors
D) b and c
E) All of the above

Accepted Answer

Although blocking neuronal activity disrupts refinement of ocular dominance column organization, it does not prevent lamina-specific targeting by RGCdendrites. This targeting appears to be determined by axon guidance cues and contact-mediated cell adhesion.

Question 6

What are the two major types of mechanisms used for wiring the nervous system? Give a specific example of each one.?

Accepted Answer

The answer of What are the two major types of...

Question 7

In the Drosophila melanogaster compound eye:
A) photoreceptors R1-R6 carry information about motion directly to the medulla.
B) photoreceptors R7 and R8 form synaptic connections in the lamina.
C) all ommatidia lacking R8 cells will also lack R7 cells.
D) all ommatidia lacking R7 cells will also lack R8 cells.
E) all ommatidia lacking R7 cells will be unable to detect blue/green light.

Accepted Answer

Rform synaptic connection in the lamina, while R7 and R8 project directly to the medulla. R7 cells detect UV light, while R8 cells detect blue/green light. R7 cell fate requires an inductive signal from R8 cells.

Question 8

Receptors of attractive cues in axon guidance and targeting include:
A) plexins.
B) Frazzled.
C) cadherins.
D) b and c
E) All of the above

Accepted Answer

Plexins are receptors for semaphorins (repulsive axon guidance cues), while Frazzled is a receptor for netrin (which can be either attractive or repulsive) and cadherins mediate homophilic cell adhesion.

Question 9

Genetic loss- and gain-of-function mosaic analysis was used to elucidate the roles of several proteins in medulla layer-specific targeting.
A. What outcome(s) would one expect in R7 vs. R8 cells from the experimental misexpression of Frazzled specifically in R7 cells?
B. What outcome(s) would one expect in R7 vs. R8 cells from a mosaic experiment in which Senseless was removed from a presumptive R7 cell?

Accepted Answer

The answer of Genetic loss- and gain-of-function mosaic analysis was...

Question 10

What is the experimental evidence that reception of information from single whiskers by stellate neurons requires cell-autonomous glutamatergic reception?

Accepted Answer

The answer of What is the experimental evidence that reception...

Question 11

Place the following events in chronological order.
A. Expression of Spineless in R7 cells
B. Expression of Boss in R8 cells
C. Expression of rhodopsins in R8 cells
D. Induction of R7 cell fate
E. Induction of R8 cell fate

Accepted Answer

The answer of Place the following events in chronological order.
A....

Question 12

What phenotype would be expected of a fruit fly with a mutation in the Ras gene that prevented its product from interacting with GAP1? Briefly explain your reasoning.

Accepted Answer

The answer of What phenotype would be expected of a...

Quiz 5: Wiring of the Visual System

Mosaic analysis studies have demonstrated that:

Which of the following general principles can be gleaned from developmental studies of the visual system in vertebrates?

The signal from R7 that induces Rh5 expression in R8 is as yet unknown. What ommatidial phenotypes would be expected of a loss-of-function mutant for the gene encoding this signal?

Both ephrins and cholinergic retinal waves appear to be necessary for normal formation of retinotopic maps in the:

Which of the following are required for retinal lamina-specific dendritic targeting by RGCs?

What are the two major types of mechanisms used for wiring the nervous system? Give a specific example of each one.?

In the Drosophila melanogaster compound eye:

Receptors of attractive cues in axon guidance and targeting include:

What is the experimental evidence that reception of information from single whiskers by stellate neurons requires cell-autonomous glutamatergic reception?

Place the following events in chronological order. A. Expression of Spineless in R7 cells B. Expression of Boss in R8 cells C. Expression of rhodopsins in R8 cells D. Induction of R7 cell fate E. Induction of R8 cell fate

What phenotype would be expected of a fruit fly with a mutation in the Ras gene that prevented its product from interacting with GAP1? Briefly explain your reasoning.