Lecture_8_Chimeras_III

Lecture_8_Chimeras_III - Re w of Le vie cture7 1. 2. 3. 4....

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Review of Lecture 7 Lineage Relationships 1. Sectorial Chimeras 2. Definitions 3. Green-white-green (GWG) periclinal chimeras 4. Laser Ablation Experiments 5. What have we learned?
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Variegation Spontaneous sectors can arise from the disruption of pigment biosynthetic genes caused by transposon insertion and excision http://faculty.ucc.edu/biology-ombrello/Images/varieg%20pothos.jpg
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Green-white-green chimeras The L2 meristematic layer is albino From Leyser and Day, Mechanisms in Plant Development. 2003 Blackwe ll Publishing,Chapter 3.
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GWG Chimeras Demonstrate that…. 1. L1 layer is very stable and rarely invades the subjacent L2 layer 2. L2 cells typically remain in the subepidermal layer in most of the leaf but near leaf margins are more likely to become displaced into the L3 3. If L2 cells invade, there is a compensatory reduction in cell divisions in the L3 so that the number of cell layers in the leaf remains constant 4. Hence one sees this fairly common pattern of variegation in garden and house plants (white margins and green centre)
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Factors affecting gene expression Location, location, location Developmental Regulation A gene may be off only if it resides in a cell in the L1 but not in the L2 (where you live matters!) Activation due to a change in fate Through cell division, an L1 daughter cell may end up in an L2 neighbourhood and hence different genes becomes activated and inactivated (turned on/off)
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Laser Ablation of the Root Tip Cell fate is determined by position
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1. Meristem layers are relatively stable (L1>L2>L3). 2. Proteins and RNAs can move between layers and there seems to be directionality. 3. Directionality is determined on a case-by-case basis. 4. There are tissue-specific constraints. L1
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This note was uploaded on 07/10/2010 for the course BIOL 321 taught by Professor Susanlolle during the Winter '09 term at Waterloo.

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Lecture_8_Chimeras_III - Re w of Le vie cture7 1. 2. 3. 4....

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