Statement I :Foreign DNA and vector DNA cut with the help of ligase.

Statement II : Ligase acts by forming phosphodiester bonds.

Only statement II is correct .

The correct answer is Option (2)-Only statement II is correct .

Statement I: This statement is incorrect. In recombinant DNA technology, foreign DNA and vector DNA are cut with the help of restriction enzymes, not ligase. Restriction enzymes cut the DNA at specific recognition sites, creating "sticky ends" that can be joined together.

Statement II: Ligase acts by forming phosphodiester bonds between the sugar-phosphate backbone of DNA molecules. After the DNA has been cut by restriction enzymes, ligase helps to join the DNA fragments together by catalyzing the formation of new covalent bonds between adjacent nucleotides, thus sealing the nick in the DNA backbone. This process is crucial in creating recombinant DNA molecules during gene cloning and other genetic engineering techniques.