470Anteriorposteriorpatterndrosophila

470Anteriorposteriorpatterndrosophila - Anterior-Posterior...

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Anterior-Posterior Pattern Formation in Drosophila Important note: Several helpful review materials are available on the FlyMove web site (http://flymove.uni- muenster.de/). Under “Processes”, you can find sections on maternal gradients and segmentation. In addition, there is a nice Flash animation in the Content section of the course web site that provides a nice overview of A-P patterning. 1. General : How do the early mitoses in the fly embryo allow for the establishment of simple gradients of proteins that might be involved in specifying pattern? [hint: what is a syncytial blastoderm ? A cellular blastoderm ?] -karyokinesis (nuclear division) occurs without cytokinesis (cell division) -rapid rate of division accomplished by eliminating G stages of cell cycle -syncytial blastoderm – no cell membranes exist other than that of the egg itself; single cell with many nuclei residing in a common cytoplasm -nuclei reach periphery of egg (10 th cycle), each nucleus is surrounded by microtubules and microfilaments -energids – nuclei and their associated cytoplasmic islands -cellular blastoderm – created after 13 th cycle; oocyte plasma membrane folds inward b/n nuclei, partitioning off each somatic nucleus into a single cell; all the cells are arranged in a single-layered jacket around the yolky core of the egg How does analysis of the cuticle and its associated denticle bands allow genetic screens to be performed in Drosophila that uncover defects in segmentation? -larva have characteristic rows of denticles at ventral side -segments in different parts of body show characteristic patterning -within each segment single cell rows can be identified through absence or presence, as well as shape of denticles -could determine mutant phenotypes by analyzing patterns -deletion of several segments – gap mutants -deletion of every other segment – pair rule mutants -pattern duplications within one segment – segment polarity mutants What classic experiments suggested that there were posterior and anterior "organizing centers" in the fly egg? -separate anterior half from posterior half of egg -one half developed into an anterior embryo and the one half developed into a posterior embryo; neither contained middle segments -showed that there are morphogenetic gradients from the two poles during cleavage, which interact to produce the spatial information of each side Principles for operation of genes regulating pattern formation? -morphogens – Bicoid and Dorsal – gradients determine specification of different cell types; can be transcription factors -temporal order – different classes of genes are transcribed, and the products of one gene often regulate expression of another gene -boundaries of gene expression – can be created be interaction b/n transcription factors and their gene targets; earlier transcribed factors regulate expression of next set of genes -translational control – extremely impt in early embryo, localized mRNAs critical in patterning embryo
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This note was uploaded on 03/27/2012 for the course ZOOLOGY 470 taught by Professor Hardin during the Spring '12 term at Wisconsin.

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470Anteriorposteriorpatterndrosophila - Anterior-Posterior...

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