Assertion (A): In order to link the alien DNA, the vector needs to have very few, preferably single recognition site for each type of restriction enzyme.

Reason (R): Presence of more than one type of recognition sequence within vector will generate several fragments which will complicate the gene cloning

Assertion is correct. In gene cloning, vectors (such as plasmids) are used to carry and replicate foreign DNA (alien DNA). To insert the foreign DNA into the vector, it is essential to cut both the vector and the foreign DNA with the same type of restriction enzyme. Restriction enzymes recognize specific DNA sequences, called recognition sites, and cut the DNA at those sites. If a vector has multiple recognition sites for the same restriction enzyme, it can result in multiple cuts, producing fragments that may not be suitable for cloning. Therefore, having very few, preferably single recognition sites for each type of restriction enzyme simplifies the gene cloning process.

Reason is incorrect. The presence of multiple types of recognition sequences within a vector does not necessarily complicate gene cloning. The potential complication arises when a single recognition sequence is repeated multiple times within the vector.

When a single recognition sequence is repeated within the vector, it can lead to multiple cuts at the same sequence, resulting in multiple fragments with the same or similar sizes. This can indeed complicate the gene cloning process because it becomes more challenging to distinguish and select the desired fragment for cloning.

Having various types of recognition sequences within the vector, as long as they are unique and do not repeat, can actually be advantageous in some cloning strategies. Different recognition sequences allow for the insertion of multiple DNA fragments at distinct locations in the vector, enabling the construction of more complex genetic constructs.

(A) is true but (R) is false