List two mutations that can result in constitutive expression ofthe lac operon in E. coli. For a given constitutiveexpression mutant, how can you determine which of these twomutations have taken place?
List two mutations that can result in constitutive expression ofthe lac operon in E. coli. For a given constitutiveexpression mutant, how can you determine which of these twomutations have taken place?
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1. The lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. The operon system is inducible in that it can be âturned onâ by the presence of lactose. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products.
These mutations include:
I - = produces a repressor protein that can not bind to the operator region
I s = produces a repressor protein that can not be removed from the operator region
O C = can not bind a repressor protein
Z - = produces a defective (non-functioning) β-galactosidase enzyme
( I- are recessive to I+; I+ recessive to IS )
Detail the functionality of the lac
operon under the following genetic and cellular conditions.
| GENES | Lactose present | Repressed (yes/no) | Constitutive (yes/no) | Inducible (yes/no) |
| I + O + Z + | no | |||
| I + O C Z + | no | |||
| I S O + Z + | yes | |||
| I - O + Z + | yes | |||
| I S O C Z + | no |
