Drosophila development Flashcards
How is the initial gradient in the oocyte formed?
C. Elegans
- Path along uterus
Xenopus
- Gravity and sperm fertilization
Drosophila
- Oocyte signals to follicle cells via EGF pathway
- Gurken signal and Torpedo receptor
- Activated follicle cells signal back
- Causes rearrangement of cytoskeleton, + at posterior
- Allows maternal mRNAs to arrange along anterior-posterior
How can the RNA vs protein be distributed in Drosophila zygote?
- RNA localized forming protein gradient
- Translational repression localizes proteins
What factors set up the anterior-posterior gradient?
- Bicoid protein anterior, encodes TF
- Nanos protein in posterior, encodes translational repressor for hunchback
- Hence maternal hunchback mRNA degraded only in posterior
What structure provides the main indicator of Drosophila phenotypes?
- Denticle bands
- Small extruding structures through shell allow insect to pull self forward
What is the anterior-posterior patterning system, and what else does it encode?
- Encoded by localized anterior Bicoid and posterior Nanos maternal mRNA
- Determines germ vs somatic cell, head vs rear and segmentation
What is the Dorso-Ventral and Terminal patterning system in Drosophila?
- Encoded by localised signals by follicle cells of dorsoventral Toll and terminal Torso
- Determines ecto- vs meso- vs endoderm
Are maternal double mutants of Drosophila in APT linear?
- Additive
What are some gap mutants?
- Kruppel, giant, knirps
What are different types of segmentation mutants?
- Gap mutants (Kruppel)
- Pair rule genes (Even-skipped)
- Segment polarity (Gooseberry)
What are trends of Gap and pair mutants?
- Encode transcription factors
- Helix-loop-helix, Zn finger, leucine zipper, homeodomain
What kind of factors are segment mutants in Drosophila?
- Variety
- TFs (engrailed)
- Signalling (wingless, hedgehog)
- Transmembrane receptors (patched)
- Cell adhesion molecules (armadillo)
- Signal transduction intermediates (shaggy)
What is the heirarchy of segmentation mutants?
- Gap genes in early pattern establishment
- Pair rule in establishing combinatorial patterns
- Segment polarity arises later in development, after gastrulation
- Signal, gradient, zones, stripes, segments
- Maternal to zygotic gradient over time
How does the engrail and wingless pair-rule pattern establish?
- Wingless protein diffuses to neighboring cells
- Causes transcription of hedgehog
- Receptor only exists away from engrailed expression
How does the engrail and wingless pair-rule pattern establish?
- Wingless causes Engrail in neighbor, which expresses Hedgehog
- Hedgehog and wingless suppress Ser in other neighbors
- Ser and Hedgehog neighbor create Rho which forms denticle belt
- Wingless inhibits Rho
