Question

Read the given statements and select the correct option.
Statement 1 : The cloning vector is required to have very few, preferably single, recognition sites for the commonly used restriction enzymes.Statement 2 : Presence of more than one recognition sites within a cloning vector will generate several fragments, which will complicate the process of gene cloning.

• A. Both statements 1 and 2 are correct
• B. Statement 1 is correct but statement 2 is incorrect
• C. Statement 1 is incorrect but statement 2 is correct
• D. Both statements 1 and 2 are incorrect

Answer 1

The correct option is A Both statements 1 and 2 are correct

When cut by the same restriction enzyme, 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 - exonucleases and endonucleases. Exonucleases remove nucleotides from the j ends of the DNA whereas endonucleases make cuts at specific positions within the DNA.Presence of more than one recognition sites within the vector will generate several 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, recognition/cloning sites for the commonly used restriction enzymes.