A cloning vector has two antibiotic resistance genes- for tetracycline and ampicillin. A foreign DNA was inserted into the tetracycline gene. Non-recombinants would survive on the medium containing :

1. ampicillin but not tetracycline

2. tetracycline but not ampicillin

3. both tetracycline and ampicillin

4. neither tetracycline nor ampicillin

A gene, whose expression helps to identify transformed cells is known as

1. selectable marker                 

2. vector

3. plasmid                                 

4. structural gene

How are transformants selected from nontransformants?

1. Presence of more than one recognition site in the vector DNA.

2. Presence of alien DNA into the vector DNA results into insertional inactivation of selectable marker.

3. Antibiotic resistance gene gets inactivated due to insertion of alien DNA.

4. Both 2 and 3.

Why is a marker gene useful?

1. It shows you whether the gene being added, has been taken up or not.

2. It's a way of labelling which gene you want to modify.

3. It sticks with the striker gene.

4.  It marks the position of r-DNA

Selectable marker helps

1.      To identify transformants

2.      To identify recombinants

3.      To identify non- recombinants

4.      To eliminate transformants