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9.17 Generalized model of Drosophila anterior-posterior pattern formation (Part 1)
9.18 Normal and irradiated embryos of the midge Smittia
9.19 Three independent genetic pathways interact to form the anteriorposterior axis of the Drosophila embryo (Part 1)
9.19 Three independent genetic pathways interact to form the anteriorposterior axis of the Drosophila embryo (Part 2)
9.20 Gradient of Caudal protein in the syncytial blastoderm of a wild-type Drosophila
embryo
In anterior regions, Bicoid binds to a specific region of caudal’s
3’UTR, thereby preventing translational of Caudal in the
anterior section of the embryo.
9.21 Control of hunchback mRNA translation by Nanos protein
9.22 A model of anterior-posterior pattern generation by the Drosophila maternal effect genes (1)
9.22 A model of anterior-posterior pattern generation by the Drosophila maternal effect genes (2)
9.23 Bicoid protein gradient in the early Drosophila embryo
9.25 Formation of the unsegmented extremities by torso signaling
Summary of anterior- posterios axis specification (page 275)
• Genes that define the anterior organizing center
• Genes that define the posterior organizing center
• Genes that define the terminal boundary regions
9.26 Three types of segmentation gene mutations (Part 1)
9.26 Three types of segmentation gene mutations (Part 2)
9.28 Expression and regulatory interactions among gap genes products
High levels of Bicoid and Hunchback induce the expression of giant, while
Kruppel transcript appears over the region where Hunchback begins
to decline.
There is a strong mutual
inhibition between
Hunchback and Knirps
and a strong mutual
inhibition between Giant
and Kruppel.
9.29 Specific promoter regions of the even-skipped (eve) gene control specific
transcription bands in the embryo
9.30 Hypothesis for the formation of the second stripe of transcription from the even-skipped gene
Even-skipped’s enhancers are composed of modular units arranged such
that each unit regulates a separate stripe or a pair of stripes.
Stripe #2 is activated by low
concentrations of bicoid and
hunchback and repressed by
both Giant and Kruppel
proteins
The differential repression events fix the positions of and the spacing
between the even-skipped stripes.
A mutation in a particular enhancer can delete its particular stripe and
no other.
The placement of the stripes can be altered by deleting the gap genes
that regulate them.
9.31 Defects seen in the fushi tarazu mutant (Part 1)
The primary pair-rule genes also form
the context that allows or inhibits the
expression of the lateracting secondary
pair-rule genes.
Early in division cell cycle 14, ftz
mRNA and its protein are seen
throughout the segmented portion of the
embryo.
However, as the proteins from the
primary pair-rule genes begin to
interact with the ftz enhancer, the
ftz gene is repressed in certain
bands of nuclei to create interstripe
regions.
9.32 Transcription of the fushi tarazu gene in the Drosophila embryo
even skipped - blue
fushi tarazu - green
9.33 Model for the transcription of the segment polarity genes engrailed (en) and wingless (wg) (1)
9.33 Model for the transcription of the segment polarity genes engrailed (en) and wingless (wg) (2)
9.33 Model for the transcription of the segment polarity genes engrailed (en) and wingless (wg) (3)
9.33 Model for the transcription of the segment polarity genes engrailed (en) and wingless (wg) (4)
9.34 Cell specification by the Wingless/Hedgehog signaling center