Lecture 11 Bio325 Fall 07

Lecture 11 Bio325 Fall 07 - One gene one enzyme: Beadle and...

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1 One gene one enzyme: Beadle and Tatum 1940’s What is an enzyme ? a molecule that catalyzes a biochemical reaction What is a biochemical pathway ? a series of biochemical reactions that create a product or accomplish a biochemical endpoint (i.e. a product, movement of cellular molecules; organization of subcellular components, etc) There are often several enzymes involved in a biochemical pathway: compound 1 2 3 4 product enzyme A enzyme B enzyme C enzyme D In a linear pathway like this one, loss of any of the four enzymes results in loss of product Fig. 7.23 auxotroph : a mutant form of a microorganism that cannot live without supplementation of a particular nutrient/growth factor prototroph : a form of a microorganism that can live without supplementation of a particular nutrient/growth factor example shown here: an arginine auxotroph must have arginine in the media in order to grow complete medium : a rich growth media with all necessary nutrients minimal medium : a defined growth media to which all necessary nutrients must be added separately
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2 addition of intermediate compounds in the arginine biosynthesis pathway identifies the relative position of each mutant in the pathway since each mutation inactivated a single enzyme, they hypothesized that one gene encodes one enzyme Consider the biosynthetic pathway for lysine in Neurospora that includes 7 enzymes: You isolate a mutant that is a lysine auxotroph. You find that it will grow if you supplement it with compounds D or E, but none of the other intermediates. Which enzyme(s) could be affected in your mutant? Your friend has mutants in all of the genes in this pathway. If you were to mate your haploid mutant with all of his mutants (#1 through #7), which combination would yield a diploid lysine auxotroph?
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This note was uploaded on 06/19/2008 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas.

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Lecture 11 Bio325 Fall 07 - One gene one enzyme: Beadle and...

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