Problem 5, 130C

Problem 5, 130C - the diploid state in which the mutant...

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Problem 5 (Due March 24) Yeast is a unicellular eukaryote with seventeen chromosomes in its nucleus that can be grown either in the haploid (with one chromosome of each type) or diploid (with homologous chromosome pairs of each type) state. Galactose metabolism is inducible in yeast, with galactose serving as the inducer. There are four structural genes involved in galactose metabolism that are dispersed in location on two different chromosomes. Two trans acting gene products (Gal4 and Gal80) regulate the expression of these four genes. A number of experiments involving mutant versions of the regulatory proteins (designated by all lower case letters) were initiated in order to shed light on the mechanisms by which they act. The following observations were made: In the majority of cases gal4 mutants were uninducible in the haploid state but inducible in
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Unformatted text preview: the diploid state in which the mutant gene is paired with wild type. • Rarely gal4 C mutants were produced in which the structural genes were expressed constitutively. • In the majority of cases gal80 mutants gave rise to constitutive expression of the structural genes. • Rarely gal80 S mutants were produced that were uninducible either in the haploid or diploid state. Based on this information, propose a model for the mechanism of the coordinated action of the regulatory proteins in the control of gal structural gene expression. Include in your discussion the potential for either repression or activation of gene transcription as well as the component of the regulatory system to which inducer binds....
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