Question

A gene is inserted into the Pvu2 site of the cloning vector and transformed into E.Coli cells. Which one the following statements is true .Recombinants are selected by plating on
a)ampicillin containing medium

b)by plating on ampicillin and tetracycline containing medium

c)either ampicillin or tetracycline containing medium.

d)only tetracycline containing medium​

Answer 1

Answer:

Only tetracyclin containg medium

Explanation:

pvu 2 is present in amphicilin resistance gene so we have to put in tetracyclin medium then transformants and non transfomants are separated.Then put into amphicilin medium recombinant and non recombinants are separated

Answer 2

The recombinants can be selected by plating them on (b) ampicillin as well as tetracycline containing medium.

(b) correct option

• This process of selecting recombinants is known as insertional inactivation.
• The PvuII site on a cloning vector is present on the ampicillin resistant gene.
• So, when a gene is inserted in that site, the ampicillin resistant gene gets disrupted and the resistance is lost.
• To select such recombinants we grow them on ampicillin as well as tetracycline containing medium.
• They will not grow on ampicillin containing medium but will grow on tetracycline containing medium as tetracycline resistant gene is intact in the recombinants.

(a) incorrect option

• If we take only an ampicillin containing medium, both the non-transformant cells (without vector) as well as the recombinants will stop growing.
• We will not be able to distinguish between those two.
• Hence, this option is incorrect.

(c) incorrect option

• As explained above, we have to take both the antibiotic mediums.
• One medium will not suffice.
• When taken on only tetracycline medium, all the recombinants will easily grow, hence no selection can be done.
• When only ampicillin medium is taken, recombinants and non transformants cannot be distinguished.
• Hence this option is incorrect.

(d) incorrect option

• Similarly, taking only tetracycline containing medium will not help in selection.
• Recombinants will have an intact tetracycline resistant gene.
• Non-recombinants will also have the same.
• So, they will both grow on such a medium.
• Hence, this option is incorrect.

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