Need to find the values of either high or low on both sides A number of mutation

Question

Need to find the values of either high or low on both sides

A number of mutations affect the expression of the lactose operon in E. coli: I^- a mutant lac repressor that cannot bind the lac operator I^s a mutant lac repressor that cannot bind lactose O^c a mutant lac operator that cannot bind repressor Lacl P^- a mutant lac promoter that cannot bind RNA polymerase Z^- a mutant lacZ lost beta-galactosidase activity Y^- a mutant permease that cannot transport lactose into the cell Consider the following strains each with the indicated mutations in the lac operon. Predict the levels of beta- galactosidase activity (either high or low) under two growth conditions: with lactose absent or present. Please assume that no glucose is present.

Explanation / Answer

absent present

1) I-P+O+Z+Y+ high high

2) I+P-O+Z-Y+ low low

3) I+P+OcZ+Y+ high high

4) IsP+O+Z+Y+ low low

5) I+P+O+Z-Y+   low low

6) I+P+O+Z+Y-   low low

7) I-P-O+Z+Y+ low low

8) IsP+OcZ+Y+ high high

9) I+P+OcZ+Y- high high

10) IsP+O+Z+Y- low low

THEORY:

if I- or Oc present then the operator of operon cannot bind repressor and produces high amounts of galactosidase at all times.

Is , P-,Z- and Y- gives low amounts of galactosidase even in the presence of lactose as it either the repressor cannot bind the lactose, promotor cannot bind RNA pol, incapable of producing the galactosidase itself or cannot transport the lactose into the cell respectively. hence the chart is justified.

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