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LECTURE 6: FORMING THE NOSE VERSUS TAIL OF A FLY. D. Tail. Skin. A. P. Nervous System (inside). Head. Thorax. Abdomen. “ Denticle ” Hairs. V. The Body Plan of a Fly Maggot. Anterior-Posterior Patterning Mutants. Dorsal-Ventral Patterning Mutants. - PowerPoint PPT Presentation
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The Body Plan of a Fly Maggot
A P
D
V
HeadThorax
Abdomen
Tail
“Denticle” Hairs
Skin
Nervous System (inside)
Fly Embryonic Patterning Mutants
Anterior-Posterior Patterning Mutants
Dorsal-Ventral Patterning Mutants
Hierarchy of Gene Action in A/P Patterning
Controlled by Mother
Segment Polarity Genes
(e.g., engrailed)
Homeotic Genes
(e.g., Bithorax)
Bicoid
Gap Genes
Controlled by Embryo
Kruppel
Pair-rule Genes
even-skipped
A P
Bicoid
A P
Homeotic
Hunchback
Even-skipped
1 26
53 4
7
Knirps
Independent Regulatory Elements Activateeven-skipped Expression in Different Stripes
71 2 3 4 5 6
even-skipped stripes
OnOff
OtherStripes
Coding RegionRegulatory Region
even-skipped mRNAStripe 2 Stripe 3
OnOffOnOff
Hb Kni
1. An activator, which is expressed everywhere, must be present.
2. Repressors, Hunchback and Knirps, must be absent.
Condition for Activating Expression of even-skipped Stripe 3
3
even-skipped stripe 3
Dorsal-Ventral Patterning Mutants
Dorsal-Ventral Patterning Mutants
D
V
High [Dorsal]
Low [Dorsal]
No Dorsal
Graded Dorsal Concentration
Created by Mother
Hierarchy of Gene Action in D/V Patterning
Mesoderm Genes
Neuronal Genes
Epidermal Genes
D/V Genes Basic Tissue Types
Controlled by Embryo
D
V
= Mesoderm = Non-Neural Ectoderm= Neuroectoderm
Epidermal GenesDpp Neuronal Genes
AS-C
Rho Ventral Epidermal Genes
Neural Genes
Twist Mesodermal GenesSnail Neural Genes
Brk, Sog Dorsal Genes
