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Developmental Cascade of 
Morphogens 
Drosophila melanogaster 
Development
Gene Expression is Regulated and Much Evolution is 
Based on Changes in Regulatory Genes
A Few Conserved Signaling Molecules are Used 
Over in Different Aspects of Development
Cascades of Induction Can Pattern an 
Entire Embryo or Embryonic Field
Drosophila Early Development is 
Syncytial
Anterior Posterior Segmentation is Mapped from 
Syncytial Blastoderm to Larva 
Hindgut & 
Internal 
organs 
Foregut & 
Int...
Drosophila Fate Map 
Gastrulation 
Movements
Anterior Posterior Determination
Only 1 gene 
inactive 
Only 1 gene 
active 
White area is 
controlled by 
Indicated gene 
Wt. Bicoid Nanos Torso 
None act...
Morphogens Are laid Down Durring 
Oogenesis
The Egg Polarity Gradient Systems
Regulatory Hierarchy of Morphogens
The “Gap” Genes, “Pair Rule” and 
“Segment Polarity” Genes
Gap Gene Proteins Maintain Gradients 
By Mutual Inhibition 
Nos 
A) bcd and nos maternal transcripts are tightly localized...
Regulation of Even Skipped by Gap Gene Products 
Gt & Kr define St 2 
Giant and Kruppel Repressors and Knirps and Hunchbac...
Regulation of Stripe 2 Promoter 
Stripe 2 Enhancer 
Eve expression 
Activators Bcd & Hb 
Inhibitors Gnt & Kr
Pair Rule and Segment Polarity Gene Expression 
Effects Structures in Adult Fly 
Expression of Segment Polarity Gene Engra...
Bicoid is a Homeobox Transcription Factor
Dorsal Side is Determined by Absence 
of “Dorsal” Protein 
D 
Dorsal protein 
Concentrated in 
Cytoplasm 
Dorsal protein V...
Protostome vs.. Duterostome 
Body Plans 
Upside Down and Backwards
Dorsoventral Morphogen Gradients
Presumptive Mesoderm Cells Express 
the Transcription Factor, Twist 
TTime
Developmental cascade of morphogens Define Drosophila Body Plan
Developmental cascade of morphogens Define Drosophila Body Plan
Developmental cascade of morphogens Define Drosophila Body Plan
Developmental cascade of morphogens Define Drosophila Body Plan
Developmental cascade of morphogens Define Drosophila Body Plan
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Developmental cascade of morphogens Define Drosophila Body Plan

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The expression of genes in specific regions of the early Drosophila embryo determine the anterior-posterior and dorso-ventral axes of the organism. Expression of these genes are both spatially and temporally coordinated.

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Developmental cascade of morphogens Define Drosophila Body Plan

  1. 1. Developmental Cascade of Morphogens Drosophila melanogaster Development
  2. 2. Gene Expression is Regulated and Much Evolution is Based on Changes in Regulatory Genes
  3. 3. A Few Conserved Signaling Molecules are Used Over in Different Aspects of Development
  4. 4. Cascades of Induction Can Pattern an Entire Embryo or Embryonic Field
  5. 5. Drosophila Early Development is Syncytial
  6. 6. Anterior Posterior Segmentation is Mapped from Syncytial Blastoderm to Larva Hindgut & Internal organs Foregut & Internal organs Anatomical Gene Exp.
  7. 7. Drosophila Fate Map Gastrulation Movements
  8. 8. Anterior Posterior Determination
  9. 9. Only 1 gene inactive Only 1 gene active White area is controlled by Indicated gene Wt. Bicoid Nanos Torso None active
  10. 10. Morphogens Are laid Down Durring Oogenesis
  11. 11. The Egg Polarity Gradient Systems
  12. 12. Regulatory Hierarchy of Morphogens
  13. 13. The “Gap” Genes, “Pair Rule” and “Segment Polarity” Genes
  14. 14. Gap Gene Proteins Maintain Gradients By Mutual Inhibition Nos A) bcd and nos maternal transcripts are tightly localized at the anterior and posterior poles of the unfertilized egg Shortly after fertilization, bcd transcripts are translated, and the resulting protein diffuses posteriorly, generating a gradient; similarly, nos transcripts are thought to generate an opposing gradient of nos (B) The hb protein gradient then provides a series of concentration thresholds that independently dictate where the anterior Kr, kni, and gt boundaries, as well as the posterior Kr boundary
  15. 15. Regulation of Even Skipped by Gap Gene Products Gt & Kr define St 2 Giant and Kruppel Repressors and Knirps and Hunchback delimit expression borders of the even-skipped stripes 3,4, 6 and 7 (see Figure 2, panel C). Two corresponding regulatory regions, 4+6 and 3+7 enhancers encode all sufficient transcriptional information for these four stripes. The eve stripes 4 and 6 are formed in the embryo zones with lower concentration of hunchback and higher concentration of Knirps, conversely the eve stripes 3 and 7 are formed where hunchback concentration is greater than that of Knirps.
  16. 16. Regulation of Stripe 2 Promoter Stripe 2 Enhancer Eve expression Activators Bcd & Hb Inhibitors Gnt & Kr
  17. 17. Pair Rule and Segment Polarity Gene Expression Effects Structures in Adult Fly Expression of Segment Polarity Gene Engrailed
  18. 18. Bicoid is a Homeobox Transcription Factor
  19. 19. Dorsal Side is Determined by Absence of “Dorsal” Protein D Dorsal protein Concentrated in Cytoplasm Dorsal protein V Concentrated in nuclei Dorsal protein binds to regulatory DNA that turns on mesoderm and nervous system genes and turns off dorsal genes
  20. 20. Protostome vs.. Duterostome Body Plans Upside Down and Backwards
  21. 21. Dorsoventral Morphogen Gradients
  22. 22. Presumptive Mesoderm Cells Express the Transcription Factor, Twist TTime

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