Which method is used to construct large, recombinant vectors when polylinker restriction enzymes are not useful?
a. recombineering
b. fish
c. gene libraries
d. yacs
e. hybridization

The correct answer will be option-A.

Explanation:

Recombineering is a molecular technique based on the recombination mechanism of DNA which is also known as recombination-mediated genetic engineering.

This method is used mainly in bacterial genetics to generate conditional mouse knockout target vector and modifying DNA in Bacterial artificial chromosome.

Since it does not use older methods like restriction enzymes and DNA ligases to combine DNA, therefore, option-A is the correct answer.