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 anterior-posterior axis of the Drosophila embryo (Part 1)

9.19 Three independent genetic pathways interact to form the anterior-posterior 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

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.

Even-skipped’s enhancers are composed of modular units arranged such that each unit regulates a separate stripe or a pair of stripes.

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