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Advanced Developmental > Drosophila Eye Development > Flashcards

Drosophila Eye Development Flashcards

1
Q

What are imaginal discs?

A

Areas which develop into the mouth, eye etc

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2
Q

When are imaginal discs set side?

A

In early embryogenesis

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3
Q

What is the haltere?

A

A balance organ

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4
Q

How many cells gather to form an imaginal disc?

A

Around 30

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5
Q

How big do structures from imaginal discs grow?

A

To about 50,000 cells

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6
Q

What is the phenotype of a Pax 6 mutant?

A

They have no eyes

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7
Q

What is eyeless?

A

A homeobox transcription factor homologous to vertebrate PAX6

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8
Q

Eyeless PAX6 is both … and … to make an eye

A

necessary

sufficient

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9
Q

PAX6 misexpressed in a fly induces what?

A

An ectopic eye

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10
Q

How many flies do drosophila have?

A

5 - 2 large and 3 small

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11
Q

What are the flies small eyes called?

A

Ocelli

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12
Q

What are ocelli used for?

A

Sense the flies orientation ie where they are in the sky

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13
Q

Each large eye consists of how many ommatidia?

A

800

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14
Q

What are ommatidia?

A

each of the optical units that make up the compound eye of an insect.

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15
Q

Why are the ommatidia hexagonal?

A

Makes them efficient in their packaging

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16
Q

Each ommatidia is associated with what?

A

A bristle involved in the cleaning process

17
Q

Why are the fly eyes curved?

A

To give them a wide plane of view

18
Q

Each ommatidia consists of:

A 
8 photoreceptors
4 cone cells
2 primary pigment cells
6 secondary pigment cells
3 tertiary pigment cells
19
Q

Why do fly eyes contain red granules around the lens?

A

They stop light from other places being scattered so light is focused in a straight line on the ommatidia

20
Q

Why does a white mutant have worse vision than a wildtype fly?

A

The white mutant has no red granules so the light scatters and confuses things

21
Q

What are rhabdomeres?

A

Light sensitive structures
They trigger neuronal input
Made of microvilli packed with rhodopsin

22
Q

How many rhabdomeres are there?

A

7

23
Q

What is the role of the equator across the eye?

A

It senses the horizon

24
Q

Where do R1 to R6 axons project into?

A

The lamina

25
Q

Where do R7 and R8 photoreceptors project to?

A

The medulla

26
Q

Why can a single object be seen by many rhabdomeres?

A

It increases resolution

27
Q

What do flies respond to?

A

Movement

28
Q

When does most growth of the eye field occur?

A

The third instar

29
Q

Photoreceptors are preceded by what?

A

The morphogenetic furrow

30
Q

Describe the morphogenetic furrow

A

Rich in actin
Moves across the disc from the posterior to the anteror
Has very few photoreceptors

31
Q

Which is the first cell to be recruited in the ommatidia?

A

R8 - they are born with in the morphogenetic furrow

32
Q

How are R8 cells recruited?

A

Using a process of lateral inhibition through Notch singalling - this inhibits other cells to become R8 cells

33
Q

Describe the order which Rhabdomeres are recruited

A

1) R8, R2 and R5 secrete EGF pathway ligand Spitz
2) R3, R4 , then R1 and R6 recruited
3) R7 is the last
4) Then cone cells are recruited after

34
Q

Mutants lacking R7 can not see what?

A

UV light

This means they go towards white light rather than UV light

35
Q

Where are R8 cells born?

A

The morphogenic burrow

36
Q

Mutations in which genes causes the loss of R7?

A

Boss and sevenless

37
Q

What does the gene sevenless do?

A

Trans membrane receptor kinase
Activator of the Ras/Raf/Erk pathway
Expressed in R8,1,6,4,3,7 and con cells

38
Q

What does Boss do?

A

A membrane tethered ligand specific to sev

Expressed eclusively in R8

Advanced Developmental (25 decks)

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