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Unformatted text preview: BICD 130 Embryos, Genes, and Development The segmented body plan of the fly The segmented body plan of the Drosophila larva is apparent at germ-band extension Progressive subdivision of the fly embryo along the A/P axis depends on a cascade of transcription factors encoded by segmentation genes The anterior patterning system of the fly embryo The posterior patterning system of the fly embryo Formation of A/P protein gradients in the early fly embryo Caudal protein Bicoid and Nanos establish opposing A/P gradients of Caudal and Hunchback by translational repression Translational repression by Drosophila Nanos A gradient of Bicoid protein Loss of bicoid function leads to loss of anterior structures morphogen: a concentration-dependent determinant of cell fate Is Bicoid a morphogen? The segmentation gene cascade switches from maternal to zygotic gene expression in the very early embryo Maternal Zygotic Sharp on/off activation of hunchback transcription by Bicoid Segments and parasegments Gap gene mutants have deletions of large multi-segment regions Gap gene expression domains subdivide the early fly embryo along the A/P axis Gap gene proteins define broad, overlapping spatial domains along the A/P axis
Hunchback Kruppel Pair-rule gene mutants have deletions of every other parasegment Seven-stripe pattern of pair-rule gene expression is the first manifestation of segmentation
fushi tarazu (ftz) Segment polarity gene mutants have deletions of parts of every segment Segment polarity genes are expressed in a defined portion of every segment
engrailed The Big Event Distinct transcriptional enhancers control each stripe of even-skipped expression Modularity of even-skipped stripe enhancers Formation of even-skipped stripe 2 requires activation by Bicoid and Hunchback, and repression by Giant and Kruppel
Hunchback eve stripe 2 Kruppel Bicoid Giant The even-skipped stripe 2 enhancer integrates multiple inputs to generate a novel output ...
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This note was uploaded on 04/29/2008 for the course BICD 130 taught by Professor Tour during the Fall '07 term at UCSD.
- Fall '07