Read the following statements and select the correct ones.
(i) Same kind of sticky ends are produced when a DNA has been cut by different restriction enzymes.
(ii) Exonucleases make cuts at specific positions within the DNA.
(iii) Hind ll was the first restriction endonuclease to be isolated.
(iv) A bacteriophage has the ability to replicate within bacterial cells by integrating its DNA with bacterial DNA.
(v) Presence of more than one recognition sites for a enzyme within the vector facilitates the gene cloning.

Options

A. (i),(iii) and (v)
B. (ii) and (iv)
C. (iii) and (iv)
D. (ii),(iii) and (iv)

Answer

C

Explanation

When cut by the same restriction enzymes, the resultant DNA fragments have the same kind of 'sticky-ends' produced, which can be joined together (end-to-end) using DNA ligase. Restriction enzymes are of two kinds -exonuclease and endonucleases. Exonucleases reomve nucleotides from the ends of the DNA wherease endonucleases make cuts at specific positions within the DNA. presence of more than one reconition sites within the vector will generate serval fragments, which will complicate the gene cloning. Therefore, in order to link the alien DNA (or foreign DNA), the vector needs to have very few, preferably single, recongnition/cloning sites for the commonly used restriction enzymes.