PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Mosaic AnalysisReading: 152-155; 731-732& lecture notesProblem set 7QuickTime™ and a decompressorare needed to see this picture.The Drosophila eyeComposed of several hundred repeating units known as ommatidiaEach ommatidium has 8 photorecetor cells, 4 cone cells, pigment cells and a sensory bristle.Drosophila eye developmentVisible UVQuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.When given a choice of light preferenceVisible UVQuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.Visible UVDrosophila prefers UVQuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.Visible UVQuickTime™ and a decompressorare needed to see this picture.Visible UVScreens for UV blind flies.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.UV blind fliesDefective in rhodopsin that detects UVMissing R7(R7 photoreceptor cell that contains UV senesitive rhodopsin)In both sev and boss mutants, R7 is missing because it is transformed into a cone cellwild-typesev- or boss-No R7If Boss is a ligand for the RTK Sevenless, then Boss’s function should be required in a cell other than R7 and Sev should be required in R7.RasIn 1936 Curt Stern observed twin spotsy+ sn / y sn+…and explained the patches by mitotic recombinationBut first a note on how mosaics were used to show how the fly eye develops.R1 R2 R3 R4 R5 R6 R7 R8Invariant lineage?Like C. elegansR1 R2 R3 R4 R5 R6 R7 R8R3 R1 R4 R7 R6 R8 R4 R5No lineage restrictions?And all other combinations!Mutant cloneAnalyze ommatidia at the periphery of mutant clone.These will be mosaic, containing both wild-type (red) and mutant (white) cells.Irradiate white/+ animals and study mosaic eyes.R1 R2 R3 R4 R5 R6 R7 R8If invariant lineage, then lineage relationships will be maintained in white clones.R1 R2 R3 R4 R5 R6 R7 R8R3 R1 R4 R7 R6 R8 R4 R5If not invariant then there will be no lineage relationships among cells in clone.This is what happens!Any cell can adopt any fate.Cells are specified entirelyby cell interactions.Etc…Boss expression is restricted to R8, but Sev is expressed in R1, R3, R4, R6, R7, the precursors to the cone cells and mystery cells.1. Does Boss function in R8 as predicted by its expression pattern?2. Does Sev function in R7, or is signaling to the R7 cell via Sev more complex?white can be used as cell autonomous marker to monitor the loss of sev.sev is required in the R7 cell; it functions cell automomouslyw-/w-; boss-/boss+ P[white+]Can use P element mediated transposition to insert white on other chromosomes.w-w-boss-P[w+] boss+boss is required in the R8 cell; it functions cell
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