33 - developmental genetics of drosophila pt. II

33 - developmental genetics of drosophila pt. II - BIOLOGY...

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BIOLOGY 325H Developmental genetics of Drosophila , Part 2 April 16, 2008 Beginning with the Heidelberg genetic screen, thousands of scientists around the world began to study the genes that are responsible in Drosophila melanogaster for a phenomenon called 'developmental pattern formation', i.e. the generation of regional differences in the embryo that foreshadow the adult body plan . In subsequent decades, nearly all of the genes involved in this process have been identified, the DNA comprising their transcription units and regulatory regions has been sequenced, and their protein products studied to ascertain when and where the protein is expressed and how it functions in the embryo. It is interesting to note that Nüsslein-Volhard and Wieschaus accurately predicted how it all worked without knowing any of those molecular details - they simply drew inferences about gene function from the abnormal phenotypes of their mutant embryos. Learning Goals 1. What are the three classes of zygotic Segmentation Genes in Drosophila , and what is the phenotype of an embryo that is homozygous null for a gene in each class? Note: I am not requiring you to memorize the individual genes, just the different classes. In what temporal order are these classes expressed during embryonic development? 2. What kind of proteins are encoded by the Gap Genes? In general, what is the spatial pattern of gap gene expression in the embryo? How does the spatial pattern of gene expression correlate with the developmental phenotype produced by null mutations of the gene? 3. What is the meaning of nucleic acid hybridization? What holds the hybrid together? Can DNA and RNA only hybridize with themselves, or can they also hybridize with one another? What must be true about the structure of two nucleic acid strands for them to hybridize with one another? 4. What is in situ hybridization, and how is it used to ascertain for an embryo or tissue sample which cells do and which cells do not express a particular mRNA? You should be able to explain the in situ hybridization staining procedure that is described in Fig. 4.16A of the additional reading. 5. What is the genetic definition of a maternal-effect gene, and how is it distinguished from a zygotic-effect gene? You should be able to solve genetic crosses involving maternal effect genes, so please practice with the questions below. 6. Many maternal-effect genes encode gene products that are referred to as ‘maternal
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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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33 - developmental genetics of drosophila pt. II - BIOLOGY...

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