Question

Lac Mutants 1-Copy 2 of 10 CAP laclCAP gene lacO lacP acolacZacY Carbon source in theLac operon p-galactosidaseLactose permease binding site me levels in levels in the cell polycistronic mRNA enzy levels in the cell Undetectable Low but detectable Low but deteteable Low but detectable medium the cell Undetectable membrane Glucose only Glucose and lactose Lactose on Another carbon source Undetectable Undetectable Undetectable Undetectable The table shows the results of experiments measuring expression of the lac operon in wild type cells grown media containing different carbon sources. Use this table as a reference for predicting the results of experiments measuring lac operon expression in the mutants descricbed in each part below. Note on gene names: CAP gene is the gene encodong the CAP protein. The CAP binding site is the DNA sequence to which CAP-CAMP binds. The lac symbols are as they are defined in the textbook. Part A What results are expected if you analyzed lac operon expression in a complete loss of function lacl mutant (acl) in medium that contained glucose as the only carbon source? O lac mRNA, Bgalactosidase and lactose permease levels would all be undetectable. lac mRNA and lactose permease levels would be high whereas B galactosidase levels would be undetectable O lac mRNA levels would all be high whereas ß galactosidase and lactose permease levels would be undetectable lac mRNA B galactosidase and lactose permease levels would all be high. O lac mRNA and B galactosidase levels would be high whereas lactose permease levels would be undetectable. lac mRNA, B galactosidase and lactose permease levels would all be low but detectable

Please solve all of them

Answer 1

A. Option A is correct.
Lac I is an inhibitor of Lac Operon.
In the absence of lacI, the operon will be constitutively expressed in the absence of glucose.
If glucose is present, the expression of the operon will be low and detectable.

B. Option E is correct.
In the absence of CAP and presence of lactose, Lac operon is activated and constitutively expressed.

C. Option D is correct.
Lac permease is required for the entry of lactose into the cell. If it is mutated, Lactose cannot enter the cell and operon cannot be active.

D. Option A is correct.
LacIs mutant cannot be suppressed by the presence of lactose. So, the operon will be constitutively repressed.