Model 1Model 2Model 2 - Gal genes Since Gal4 positively...

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Model 1Model 2Model 2 Put together the simplest model is that Gal4 is a positive regulator of Gal1 (and the other Gal genes). The + sign indicates that Gal4 increases Gal expression, but does not indicate whether this is direct or indirect. Gal80 mutant : The next useful regulatory mutant isolated was Gal80 - , in which the Gal1 encoded galactokinase is expressed even in the absence of galactose and is not further induced in its presence. Again, heterozygous diploids ( Gal80 - /wt ) showed that Gal80 - is recessive, Tetrad analysis showed that Gal80 is not linked to Gal1 , Gal4 or any of the Gal genes. If a mutant Gal80 results in constitutive Gal1 expression, the simplest model is that Gal80 negatively regulates the
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Unformatted text preview: Gal genes. Since Gal4 positively regulates, and Gal80 negatively regulated Gal1 expression, we have to figure out how these two gene products work together to achieve such regulation. Assuming that Gal4 and Gal80 act in series there are two formal possibilities: Model 1 is that Gal4 positively regulates Gal1 , and that Gal80 negatively regulates Gal4 ; the presence of galactose somehow inhibits Gal80 function thus releasing Gal4 to positively activate Gal1 expression. Model 2 is that Gal80 negatively regulates Gal1 , and Gal4 negatively regulates Gal80 ; here the presence of galactose positively activates Gal4 which in turn negatively regulates Gal80 , thus relieving inhibition of Gal1 expression....
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This note was uploaded on 11/05/2011 for the course BIOLOGY MCB2010 taught by Professor Jessicadigirolamo during the Fall '10 term at Broward College.

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