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Fly Embryonic Patterning Mutants
Anterior-Posterior Patterning Mutants
Hierarchy of Gene Action in A/P Patterning
Bicoid
Controlled
by Mother
A
P
Gap Genes
Controlled
by Embryo
Kruppel
Pair-rule Genes
even-skipped
Segment Polarity Genes
(e.g. engrailed)
Homeotic Genes
(e.g. bithorax)
Bicoid
A
P
Hunchback
1
Knirps
2
6
3 4 5
Even-skipped
Homeotic
7
Independent Regulatory Elements Activate
even-skipped Expression in Different Stripes
1
2
3
4
5
6
7
even-skipped stripes
OtherStripes
Off
On
Stripe 2
Off
even-skipped mRNA
Stripe 3
On
Off
Regulatory Region
On
Coding Region
Condition for Activating Expression of
even-skipped Stripe 3
1. An activator, which is expressed everywhere, must be present.
2. Repressors, Hunchback and Knirps, must be absent.
Hb
Kni
3
even-skipped stripe 3
Fly Embryonic Patterning Mutants
Dorsal-Ventral Patterning Mutants
Hierarchy of Gene Action in D/V Patterning
Graded Dorsal Concentration
D/V Genes
Basic Tissue Types
D
No Dorsal
Non-neural Genes
Low [Dorsal]
Neuroectoderm Genes
High [Dorsal]
Mesoderm Genes
V
Created by Mother
Controlled by Embryo
Dpp
Epidermal Genes
Neuronal Genes
Dorsal Genes
Brk, Sog
AS-C
Neural Genes
= Mesoderm
Rho
Ventral Epidermal Genes
Snail
Twist
Neural Genes
Mesodermal Genes
= Neuroectoderm
= Non-Neural Ectoderm