A recombinant protein is to be expressed under the control of the lac promoter and operator in a strain of E. coli having the genotype lacI⁺ crp⁺. Even in the absence of inducer IPTG, low levels of expression of the recombinant protein are seen (leaky expression). Which one of the following should be done to minimize such leaky expression?

If bacterial cells are transformed with a mixture of linear and circular molecules resulting from a ligation reaction designed to produce a recombinant molecule

A. No recombinant molecule will ever be detected

B. Both linear and circular molecules will replicate equally well

C. None of the plasmids will express the antibiotic resistance gene located on the plasmid

D. The circular molecules will be amplified by the cells

A recombinant protein is to be expressed under the control of the lac promoter and operator in a strain of E. coli having the genotype lacI⁺ crp⁺. Even in the absence of inducer IPTG, low levels of expression of the recombinant protein are seen (leaky expression). Which one of the following should be done to minimize such leaky expression?

A. Addition of lactose to the medium

B. Removal of all glucose from the medium

C. Addition of excess glucose to the medium

D. Addition of allo-lactose to the medium

Determine the correctness or otherwise of the following Assertion [A] and the Reason [R].
Assertion [A]: Dam methylase protects E. coli DNA from phage endonucleases.
Reason [R]: E. coli Dam methylase methylates the adenosine residue in the sequence "GATC".

A. Both [A] and [R] are true and [R] is the correct reason for [A]

B. Both [A] and [R] are true but [R] is not the correct reason for [A]

C. Both [A] and [R] are false

D. [A] is false but [R] is true

The schematic of a plasmid with a gap in one of the strands is shown below:
Which of the following enzyme(s) is/are required to fill the gap and generate a covalently closed circular plasmid?
P. DNA ligase
Q. Alkaline phosphatase
R. DNA polymerase
S. Polynucleotide kinase

A. P only

B. P, R and S only

C. P and R only

D. P, Q and R only