Different nuclear concentrations ofthe maternally deposited proteinDorsal determine the different fatesalong the D/V axis9.15 Subdivision of the Drosophila dorsal-ventral axis by the gradient of Dorsal proteinin the nucleishort gastrulationmorphogen:A concentration-dependentdeterminant of cell fateThe genetics of axisspecification in DrosophilaExtended germ band stage and germband retractionForward genetics: from mutant to geneThe logic behindthe Anterior-posterior axispatterning:Progressive subdivisionof the fly embryo alongthe A/P axisThe anterior-posterior axis is specifiedduring oogenesis (Part 1)Formation ofA/P proteingradients inthe early flyembryoCaudal proteinMaternalZygoticThesegmentationgene cascadeswitches frommaternal tozygotic geneexpression inthe very earlyembryoGap gene mutants have deletionsof large multi-segment regionsGap gene expression domains subdividethe early fly embryo along the A/P axisPair-rule gene mutants have deletionsof every other parasegmentSeven-stripe pattern of pair-rule gene expressionis the first manifestation of segmentationfushi tarazu (ftz)Fig. 9.31 Defects seen in the fushitarazu mutantGroup activity: What is an enhancer?Which of the following statements describe anenhancer?1. An enhancer is a transcription factor2. An enhancer is a piece of DNA that regulatesgenes activity3. An enhancer is part of the protein that enhancestranscription4. An enhancer is part of the mRNA that enhancestranslationGroup activity: What is an enhancer?1. A gene can have only one enhancer2. An enhancer can be found only ustream to thegene it regulates3. An enhancer is the sequence that binds RNApolymerase4. An enhancer is a DNA sequence that bindstranscription factors. Those could be repressors oractivators of transcription.Distinct transcriptional enhancers controleach stripe of even-skipped expressionModularity of even-skipped stripe enhancersFormation of even-skipped stripe 2 requiresactivation by Bicoid and Hunchback, andrepression by Giant and KruppelKruppelGiantBicoidHunchbackeve stripe 2The even-skipped stripe 2 enhancer integratesmultiple inputs to generate a novel outputSegment polarity gene mutantshave deletions of parts of everysegmentengrailedSegment polarity genes are expressedin a defined portion of every segmentRegional expression of homeotic (Hox)genes defines segment identityHox genes allencodehomeodomaintranscriptionfactors9.38 Antibody staining of the Ultrabithoraxprotein in (A) the wing disc and (B) the halteredisc of third instar Drosophila larvaeLoss of Ubx function in T3 yields a four-winged flyEd LewisMisexpression of Antennapedia in the headcauses an antenna-to-leg