Question

A DNA cloning vector should possess

• A. ori
• B. selectable marker
• C. multiple cloning sites
• D. all of these

Answer 1

The correct option is D all of these

The DNA used as a carrier for transferring a fragment of foreign DNA into a suitable host is called vehicle or vector DNA.

A DNA cloning vector should possess:

1. Origin of replication (ori): This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also responsible for controlling the copy number of the linked DNA. So, if one wants to recover many copies of the target DNA, it should be cloned in a vector whose origin support high copy number.

2. Selectable marker: In addition to 'ori', the vector requires a selectable marker. Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E. coli.

3. Cloning sites: In order to link the alien DNA, the vector needs, recognition sites for the commonly used restriction enzymes. The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes.