Question

What are the essential features of a cloning vector?

Answer 1

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Here's your answer...

Essential features of a cloning vector are as follows :-

1. Origin of replication

This DNA sequence is not only

essential for origin of replication but responsible for controlling the copy number of linked DNA.

2. Selectable markers

The vector requires a selectable marker for identifying and eliminating non- transformants.

3. Cloning sites

For linking the alien DNA, the vector requires a single recognition sites for the restriction enzymes

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Answer 2

Question:

What are the essential features of a cloning vector?

Answer:

Features of cloning vector :

(i) 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.

(ii) Selectable marker : It wil help in identifying and eliminating non-transformants and selectively permitting the growth of the transformants. Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin are considered useful selectable markers for E.coli.

(iii) Cloning sites : The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes. We ligate the foreign DNA at BamH I site of tetracycline resistances gene in the vector PBR322. The recombinant plasmids will lose tetracycline resistance due to insertion of foreign DNA. The transformants can be selected from the non-transformants by growing the bacteria on ampicillin containing medium. The recombinants will grow in ampicillin containing medium but not on tetracycline containing medium.

(iv) Size of vector : Should be small as large molecules have tendency to breakdown during purification.