Appendage formation

20 important questions on Appendage formation

What is an imaginal disc

Images of adult stage found in larva, mostly anterior. Other term is organ primordia

How is development of imaginal discs regulated

Through master genes, that induce a lot of pattern formation, differentiation and specialization

What organs have imaginal discs

Mouthparts, antenna, eye, leg, haltere, wing, genitalia
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What 3 parts is the wing made of

Wing blade, hinge and notum

How do imaginal discs form

From ectodermal invaginations, they then grow by division and develop according to the segment they were located in

What happens during wing blade development

Dorsal folds over ventral during metamorphosis

What protein is always in the posterior compartment

Engrailed

What happens in engrailed mutants

Ablation of compartment boundaries

What does engrailed do in wing blade

Only posterior expression, induces Hedgehog (Hh) expression

How far does a Hh gradient reach

No more then 10 cells

Where is the Hh pathway active in wing blade

Anterior, since this is the place with most Ci. But since Hh does not reach all wing, it is the posterior part of the anterior compartment

What is important about compartment boundary

Restricts cell movement but not secreted proteins

What is one of the Ci targets

Dpp

What is common for al Dpp targets

All TFs that determine cell fate

What molecule is important for restricted diffusion

HSPGs, proteoglycan rich ECM protein

How can the effect of the morphogen be influenced by recieving cells

The concentration of receptors can play a huge role in the effect of morphogens. Even if the concentration is very low due to the gradient, a high receptor concentration can still give a large effect of this small concentration

What can Hh or Dpp mutants do

Cross the compartment boundaries

What gene is important for dorso-ventral wing boundary

Apterous, expressed at the dorsal compartment

Where is Notch active in the wing

At the DV boundary, it induces Wingless here

What does Wg do in wing

Together with Notch it controls expression of BE (boundary enhancer) that controls Vestigial. Vestigial is expressed in all of the quadrants, only not at the compartment boundaries

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