32 - developmental genetics of drosophila pt. I

32 - developmental genetics of drosophila pt. I - BIOLOGY...

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BIOLOGY 325H Developmental genetics of Drosophila , Part I April 14, 2008 One of the most powerful tools for understanding biological systems is the genetic screen, a methodology which seeks to identify previously unknown genes that have some specific function or are associated with a particular process. A central component of genetic screens is the production and characterization of large numbers of random mutations, thereby providing the experimenter with an unbiased means of looking for new genes based solely on function. This procedure has been used with great success to analyze the genetic basis of complex biological phenomena such as behavior and development. There is one downside to genetic screens: i.e. they require that a large number of individual organisms be maintained and bred carefully over several generations. As a result, genetic screening is generally limited to species that are easily maintained in the lab and have a relatively short generation time. We will first consider some of the general features of the screening procedure, and then focus on the design and outcome of the so-called "Heidelberg screen' in which Nüsslein-Volhard and Wieschaus first elucidated the genetic basis of how the adult body plan gets laid down in the egg and embryo of the fruitfly Drosophila melanogaster. Learning Goals 1. What is mutagenesis? When an adult animal is subjected to mutagenesis for the purposes of a genetic screen, which specific cells are the targets of mutation? Do the offspring of a mutagenized adult carry the same or different mutations? Why? 2. The vast majority of mutations cause a loss-of-function in the mutated gene, and most of those are recessive to wild-type. How does an "F 3 screen" address this problem, and allow the experimenter to identify mutant alleles by phenotype? Why does it take three generations? You should be able to describe the steps in an F 3 screen, and also explain why each step is necessary. 3. What is the purpose of using genetic markers in a genetic screen (or other breeding
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This note was uploaded on 05/14/2008 for the course BIO 325H taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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32 - developmental genetics of drosophila pt. I - BIOLOGY...

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