Drosophila Wing Development Quiz

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Questions and Answers

What role does Tbx5 play in limb development?

  • Specifies forelimb identity (correct)
  • Activates FGF10
  • Activates Tbx4
  • Induces AER formation

What happens when FGF is present in limb development?

  • It leads to proximal truncation of the limb.
  • It inhibits limb bud formation.
  • It activates the polarizing region. (correct)
  • It prevents the activation of AER.

Which of the following accurately describes the AER's function in limb development?

  • Essential for proximal-distal limb growth. (correct)
  • Responsible for specifying hindlimb identity.
  • Promotes anterior-posterior patterning.
  • Induces limb trunkation when absent.

What does the polarizing region influence in limb patterning?

<p>Specifies digital patterns like pinky versus thumb. (B)</p> Signup and view all the answers

How do FGF10 and FGF8 relate to the AER?

<p>They facilitate the formation of the AER. (A)</p> Signup and view all the answers

What is the role of vestigial in wing development?

<p>It is a co-activator necessary for wing development. (B)</p> Signup and view all the answers

How is the leg imaginal disc structured?

<p>It extends like a collapsed cone. (D)</p> Signup and view all the answers

What signals are involved in the initiation of limb bud development?

<p>Initial signals from the mesoderm and ectoderm. (A)</p> Signup and view all the answers

What is required for the formation of particular leg regions?

<p>The dachshund gene. (B)</p> Signup and view all the answers

What occurs when hox genes are expressed in the wrong location in the imaginal disc?

<p>The imaginal disc will grow incorrectly. (A)</p> Signup and view all the answers

What defines the outer layer of the limb bud?

<p>An epithelium known as the apical ectodermal ridge. (A)</p> Signup and view all the answers

Which signaling pathway is essential in the early phase of wing development?

<p>Wingless and Notch signaling. (A)</p> Signup and view all the answers

What does the apical ectodermal ridge do in limb development?

<p>Acts as a zone of proliferating cells. (B)</p> Signup and view all the answers

What role do hox genes play in organogenesis?

<p>They control the segmentation and development of imaginal discs. (A)</p> Signup and view all the answers

How does hedgehog (Hh) function as a morphogen in the Drosophila wing disc?

<p>It creates a protein gradient that influences cell fate. (A)</p> Signup and view all the answers

What is the significance of the Dpp gradient in wing development?

<p>It activates transcription factors and patterns the wing along the A-P axis. (D)</p> Signup and view all the answers

What does the term 'vestigial' refer to in the context of Drosophila wing development?

<p>A transcription factor that integrates various enhancers for wing development. (A)</p> Signup and view all the answers

What happens if cells in the imaginal disc are removed or destroyed?

<p>The remaining cells will regenerate correctly. (C)</p> Signup and view all the answers

What is the function of the apterous selector gene in Drosophila wing development?

<p>It induces expression of notch ligands in adjacent cells. (A)</p> Signup and view all the answers

Which of the following proteins are involved in the posterior expression patterning in Drosophila wing discs?

<p>Ci and Dpp. (D)</p> Signup and view all the answers

What is the primary outcome of A-P patterning in Drosophila wings?

<p>Establishment of vein patterns. (C)</p> Signup and view all the answers

Flashcards

Imaginal discs

Embryonic ectoderm structures that remain until metamorphosis and develop into specific adult structures.

Hox genes

Genes that determine the body plan of an organism during development, such as deciding segments.

Dpp morphogen gradient

Protein gradient in Drosophila wing that helps pattern the wing along the anterior-posterior axis.

Signalling center

A special region that sets up signals to direct development of structures like the wing of a fly.

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Vestigial TF (transcription factor)

A protein that controls genes needed specifically for wing development.

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Anterior-Posterior (A-P) patterning

The process of establishing the front-to-back axis in developing organs.

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Morphogen

A signaling molecule that establishes a concentration gradient, directing cell behavior.

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Selector genes

Genes that are always on and set the stage for other genes to turn on to generate a specific part of the body.

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What determines limb type?

The combination of Hox genes expressed in the lateral plate mesoderm determines whether a forelimb or hindlimb develops. Tbx5 is activated for forelimbs, while Tbx4 is activated for hindlimbs.

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AER

The Apical Ectodermal Ridge (AER) is a signaling center located at the tip of the limb bud. It is crucial for proximo-distal development, meaning the development of the limb from shoulder to fingertips.

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FGF signaling

Fibroblast Growth Factors (FGFs) are signaling molecules that play a crucial role in limb development. FGF10 and FGF8 are key players in the formation of the AER.

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Polarizing region

The polarizing region is located on the posterior side of the limb bud. It is essential for A-P patterning, meaning the development of the limb along the anterior-posterior axis (thumb to pinky).

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What happens if the AER is removed?

If the AER is removed, the limb will develop only up to the point where the AER was removed, resulting in limb truncation. This demonstrates that the AER is essential for proximo-distal development and limb growth.

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Vestigial Gene

A transcription factor essential for correct wing development in Drosophila, meaning without it, normal wings won't form. It works by interacting with other crucial proteins to regulate wing-specific genes.

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What turns on vestigial early in development?

The Notch and Wingless signaling pathways activate vestigial in the early stages of wing development using a boundary enhancer.

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How is vestigial activated later?

In the later stages, Wingless and Dpp (Decapentaplegic) signaling pathways turn on vestigial, resulting in its expression throughout the entire wing disc.

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Imaginal Discs in Drosophila

These are pockets of cells in the larva that remain dormant and develop during metamorphosis into adult structures like wings, legs, and antennae. They essentially provide the blueprint for the organism's adult features.

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Leg Disc Pattern

Drosophila leg imaginal discs are patterned similarly to the wing disc, with the leg disc resembling a collapsed cone. They are comprised of epidermal cells that join together to form the leg's segments.

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How is the leg disc patterned? (A-P axis)

The A-P (anterior-posterior) axis of the leg disc is patterned by the expression of various signaling molecules, including Hedgehog (Hh), Engrailed (En), and Ap (apterous), which are expressed in specific regions, directing the fate of the cells.

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Dorsal-Ventral (D-V) Patterning in the Leg

The D-V axis of the leg is established by the expression of two crucial signals - Wingless (Wg) on the ventral side and Dpp on the dorsal side. These interactions help define the distinct regions of the leg.

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Limb Buds

These are small outgrowths that emerge from the body wall of the embryo, giving rise to the adult limbs. They are comprised of two main components: a mesenchymal core and an outer epithelial layer.

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Study Notes

Organogenesis

  • Imaginal discs develop from the embryonic ectoderm and persist until metamorphosis.
  • Segments develop using nox genes.
  • If cells in a disc are removed, the disc can regrow correctly.
  • Parallel evolution results in similar traits evolving independently.

Adult Wing

  • Wings emerge at metamorphosis after the folding and evagination of imaginal discs.
  • The wing turns inside out, extending outward, with dorsal and ventral surfaces.
  • Wings are divided into A/P (anterior-posterior) compartments.
  • The wing imaginal disc has cells that determine the notum and hinge but not the wing itself.
  • vestigial is a transcription factor co-activator expressed only in the wing, sufficient for wing development.
  • Wing development is promoted by Notch and Wingless signaling.

Dpp Patterns in Drosophila Wing Disc

  • Expression of patterning genes responds to signaling centers at the A/P boundary.
  • engrailed and hedgehog genes are in the posterior of the imaginal disc.
  • Signaling molecules (including Dpp- morphogen) are involved in patterning.
  • Selector gene expression begins with pair-rule genes and stays on.
  • Hedgehog acts as a morphogen, starting in the posterior, and diffuses.
  • There are posterior and anterior compartments.

D/V Compartment Patterns in Drosophila Wings

  • apterous, expressed throughout development, induces the expression of serrate (a Notch ligand).
  • Delta is expressed in dorsal compartments.
  • serrate and wingless expression forms a stripe in the middle.

Vestigial Expression

  • Wingless plus vestigial stripe down the center.
  • Vestigial is a transcription co-activator necessary for wing development.
  • Vestigial gene expression is influenced by boundary enhancers, and the early expression depends on wingless & notch.

Drosophila Leg Disc

  • Imaginal leg discs are cone-shaped.

  • Leg discs have different rings, similar to wings.

  • Dpp is expressed dorsally and Wingless ventrally.

  • Distal-less mutation disables distal development.

  • Hox genes are responsible for directing the formation of particular leg regions.

Limb Buds

  • Small protrusions from the embryo's body.
  • Limbs have 3 axes: dorsal/ventral, anterior/posterior, and proximal/distal.
  • Early limb buds have a mesenchymal core and an outer epithelial layer.
  • Ectodermal ridge thickening directs limb development.
  • Limbs differentiate as they extend from proximal to distal.

Genes and Lateral Plate Mesoderm

  • Lateral plate mesoderm genes influence limb type.
  • Combinatorial Hox code in the lateral plate mesoderm defines limb placement.

FGF Signaling (General Points)

  • FGF is a signaling molecule that influences limb formation.
  • FGF is important for AER formation, crucial for proximo-distal development.
  • FGF is used to determine the presence or absence of AER, which plays a role in limb development.
  • FGF signaling involves positive feedback loops.
  • Removing AER results in limb truncation.

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