Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

UVic BIOL 309 - Spring 2019 > Eye Development > Flashcards

Eye Development Flashcards

1
Q

How many times are eyes thought to have evolved?

A

At least 40-50 times.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What condition results in a “small eye” mutant mouse? Does it come from a heterozygous or homozygous mutation?

A

Microphthalmia. Comes from a heterozygous mutation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is anophthalmia? Does it come from a heterozygous or homozygous mutation?

A

A total loss of eye, nose, and brain structures (die at birth). Basically a homozygous version of microphthalmia.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What gene is responsible for producing “small eye” mutant mice?

A

Pax6 (encodes a homeodomain TF).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What steps outline early eye formation in mice?

A
  1. Evagination of optic vesicles
  2. Invagination of lens placode
  3. Forms optic cup with pinching off of optic vesicle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is aniridia? What are the morphological characteristics?

A

The human version of microphthalmia in mice. Missing an iris, cloudy lens, under-developed retina.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Is Pax6 gene dosage important for eye development? What happens if you have too much? Too little?

A

Yes. Adding Pax6 to “small eye” mutant can rescue development.
Excess = “small eye” mutant
Lack = “small eye” mutant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is Pax6 gene dosage controlled in the eye? How did Bridget’s experiments determine this?

A

Controlled by ~12 miRNAs. Determined using a PITA to predict potential miRNA and then narrowed the range from here.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens if you knock out one of the miRNA binding sites for Pax6? What if you knock out both?

A

No effect with just one knock-out. miRNA repression lost and Pax6 over-expressed if both knocked out.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does miRNA -> Pax6 binding site knockout tell us about the miRNA function in regulating Pax6?

A

miRNA must function in a cooperative, redundant manner.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What kinds of eyes do drosophila have? What kind of photoreceptors do they have?

A

Compound eyes with rhabdomeric photoreceptors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What kind of photoreceptors do protostomes have? What about deuterostomes?

A

Protostomes: rhabdomeric
Deuterostomes: ciliary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What differentiates rhabdomeric photoreceptors from ciliary photoreceptors?

A

Rhabdomeric express opsins in the microvilli while ciliary express opsins in a modified cilium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How were researchers able to induce ectopic eye expression in drosophila?

A

Using the GAL4 UAS system to express “eyeless” in the legs and antennae, and wings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What gene is critical for eye development in drosophila? What about mice? Are these functionally conserved?

A

Drosophila: eyeless
Mice: Pax6
Yes. Replacing one with the other has little effect.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Is Pax6’s function as a master control gene conserved in vertebrate development?

A

Yep, also induced ectopic eyes on Xenopus when tested by Bob :)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

In the vertebrate eye, what does misexpression of Optx2 cause?

A

Formation of “big” eyes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

In the vertebrate eye, what does misexpression of Rx cause?

A

Expansion of eye structures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Does Pax6 act alone as the “dictator” of eye expression?

A

No. Acts as a key member of a larger “junta” which controls eye development.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Once the regulatory eye-specific TF network begins, does it require continuous stimulation?

A

No, can upregulate itself to direct eye development independently.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How did eye structures evolve in protostomes and deuterostomes?

A

Protostomes and deuterostomes likely shared a single ancestor with both kinds of opsins and signalling pathways.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the implications of protostomes and deuterostomes having a common ancestor with both kinds of opsins and signalling pathways?

A

Some protostomes have ciliary opsins while some deuterostomes have rhabdomeric opsins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What early optic cup tissue is the retina derived from?

A

The pseudostratified neuroepithelium.

24
Q

How does the pseudostratified neuroepithelium grow? What is this process called?

A

Undergoes cell division but only at the apical side. Cell nuclei can move from one side to the other by “interkinetic nuclear migration”.

25
Q

What gene is involved in retina formation that is only expressed in the retina?

A

Chx10.

26
Q

Why do mutations in Chx10 affect the development of the whole eye if Chx10 is only expressed in the retina?

A

Because the retina can influence the development of the cornea and lens.

27
Q

Where on Chx10 is the mutation causing mouse microphthalmia? What kind of mutation is it?

A

A nonsense mutation at the beginning of the homeodomain.

28
Q

Where on Chx10 is the mutation causing human microphthalmia? What kind of mutation is it?

A

A nonsense mutation in the middle of the homeodomain.

29
Q

When does the vertebrate lens stop growing?

A

It never does, but growth slows to a crawl later in life (think “tree trunk” analogy).

30
Q

What 2 components make up the vertebrate lens? What happens if you invert the lens (in a young organism)?

A

Think “tree trunk” analogy!

  1. Lens epithelium (“bark”)
  2. Fibre cells(“core”)

Inversion causes the cell types to switch, eventually becomes a viable eye again.

31
Q

How does Chx10 interact with Kip1 (+Cdk2/cyclin D2) to regulate retinal development?

A

In a double-negative gate.

Chx10 -| Kip1 -| Cdk2 -> cell cycle continues

32
Q

If Chx10 were nonfunctional, what would likely occur regarding Kip1 and the cell cycle?

A

Kip1 (normally inhibited) would inhibit Cdk2/cyclin D1, causing cells to go to G0 prematurely and resulting in a small eye.

33
Q

What occurs when retinal cells exit the cell cycle and go to G0?

A

They differentiate into the different retinal cell types.

34
Q

How does Chx10 regulate Kip1 (i.e. at what level)?

A

At the protein translation level.

35
Q

What happens to retinal development in mice if both Chx10 and Kip1 are missing?

A

Would expect huge eyes, but actually get a rescue and more-or-less normal eye development.

36
Q

What occurs to a mouse which has a Chx10 mutation causing loss of bipolar cells?

A

That mouse is blind because no photoreceptor signals are reaching the ganglion cells.

37
Q

What are the 2 functional roles of Chx10?

A
  1. Regulation of cell-cycle exit

2. Specification of bipolar cells

38
Q

How are retinal cell fates determined? Unique progenitors? Multipotent progenitors?

A

Actually limited potency progenitors. Differentiation partially controlled by temporal ordering.

39
Q

Which 4 retinal cell types differentiate earlier in development?

A
  1. Ganglion
  2. Amacrine
  3. Cone
  4. Horizontal
40
Q

Which 3 retinal cell types differentiate later in development?

A
  1. Rod
  2. Bipolar
  3. Muller Glia
41
Q

What transcription factor regulates retinal progenitor multipotency? What retinal cell type is this not required for?

A

Pax6. Not required to specify amacrine cells though.

42
Q

What are the 2 ways to control retinal cell specification?

A
  1. Basic helix loop helix

2. Homeodomain TFs

43
Q

What are the symptoms of retinal degeneration?

A

Photoreceptor loss, progressive vision loss leading to eventual blindness.

44
Q

What are the 4 challenges associated with retinal cell transplantation therapies?

A
  1. Generation of target cells
  2. Integration with retina
  3. Synapse formation
  4. Visual signalling
45
Q

What is cyclopia?

A

You just get one big eye in the middle of your face instead of two…

46
Q

How does cyclopia occur? What TFs are involved in this?

A

A failure of the early eye-field to split into two separate eyes. Pax6 and Pax2 implicated.

47
Q

What mechanism causes the early eye-field to split?

A

The growth of the prechordal plate mesoderm inhibits medial Pax6.

48
Q

How does the prechordal plate mesoderm inhibit Pax6?

A

By expressing shh that stimulates Pax2 to transcriptionally repress medial Pax6.

49
Q

What eye development defect arises from the loss of shh expression?

A

Holoprosencephaly. Failure of face/brain to divide into R and L halves.

50
Q

What molecule was causing farm animals to give birth to offspring expressing cyclopia?

A

Certain plants have cyclopamine which actually inhibits smoothened activity in the shh pathway.

51
Q

How did blind cavefish lose their eyes?

A

They have expanded shh expression and therefore broad inhibition of Pax6 (no eyes).

52
Q

Why might repression of Pax6 and upregulation of Pax2 be advantageous for cave fish?

A

shh and Pax 2 linked to ear development. But cave fish actually have worse hearing that helps them block out ambient noises which interfere with important sounds.

53
Q

Why does reversal of the lens actually have no effect in the long run?

A

Because there are factors in the cornea and surrounding tissues that determine proliferation and differentiation of lens cells. They eventually change cell type to become the other, restoring function.

54
Q

What occurs to mouse eye development if Chx10 is present but Kip1 is non-functional?

A

The mouse develops big eyes (up to a point).

55
Q

What 2 factors keep retinal progenitor cells in a proliferative state?

A
  1. Sonic hedgehog

2. Notch

UVic BIOL 309 - Spring 2019 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions