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Unformatted text preview: Given below are the genotypes of five haploid lac mutants; i.e., the affected genes and sites are arranged in the cis configuration. Allocate the appropriate phenotype, listed under A - C, to each genotype, listed under 1 -5. Genotype
1. lacI o + Z + 2. lacI S o + Z + 3. lacI + o c Z + 4. lacI s o c Z + 5. lacI s o c Z Penotype
A. Lac + inducible B. Lac + constitutive C. Lac Given below are the genotypes of six lac merodiploids, i.e., the mutant alleles of affected genes and sites are arranged either in the cis or the trans configuration. Allocate the appropriate phenotype, listed under A - C, to each genotype. Assume there is no glucose in the medium. 1. lacI o+ Z+ lacI + o + Z lacI + o C Z + lacI S o + Z + 2. lacI S o + Z + lacI + o + Z + lacI + o C Z lacI d o + Z + 3. lacI o+ Z+ lacI + o C Z lacI rc o + Z lacI + o C Z + 4. 5. 6. A. B. C. D. Lac + inducible Lac + constitutive Lac Lac+, repressed by IPTG Phenotypes Some HEY THERE Questions!
1. The lacZ gene is used as a "reporter" gene in plasmids used to clone DNA. How come the expression of lacZ can be induced by IPTG even when the cells are growing in L-broth, which contains "tons" of glucose? 2. Is it possible to get mutations that affect components of the positive control system of the lac operon that result in the induction of lacZ by IPTG in the presence of glucose? 3. Is it possible to produce an E. coli strain that is dependent on glucose as its carbon source (i.e., can not carbohydrates other than glucose as carbon sources)? 4. What kinds of mutations might result in the constitutive expression of the araBAD genes in the absence of glucose? 5. What kinds of mutations could result in the constitutive expression of the arginine operon? 6. What kinds of mutations would produce a "non-inducible" arginine operon? ...
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This note was uploaded on 05/01/2010 for the course MMG 431 taught by Professor Bertrand during the Spring '08 term at Michigan State University.
- Spring '08