Given below are two columns. In Column I is the list of four enzymes and in Column II is the list of functions of the given enzymes. Which one of the following options shows the enzymes matched with their respective functions correctly ?

The correct option is P-iii, Q-i, R-ii, S-iv.

To find the correct match between Column I (Enzymes) and Column II (Functions) from the provided image, we analyze each enzyme's function step-by-step:

P. DNA Ligase: DNA ligase is an enzyme that repairs single-strand breaks in double-stranded DNA and joins DNA fragments together. It does this by catalyzing the formation of a phosphodiester bond between the 3'-hydroxyl group of one nucleotide and the 5'-phosphate group of another. Therefore, P matches with iii (Joins the DNA fragments).

Q. Restriction exonuclease: Exonucleases are enzymes that catalyze the cleavage of nucleotides one by one from the ends of a polynucleotide chain. Specifically, a restriction exonuclease acts at the terminal ends of DNA to remove nucleotides. Therefore, Q matches with i (Removes nucleotides from ends of DNA).

R. Taq polymerase: Taq polymerase is a heat-stable DNA polymerase isolated from the thermophilic bacterium Thermus aquaticus. It is widely used in polymerase chain reactions (PCR) to synthesize a complementary DNA strand by extending a primer bound to a DNA template. Therefore, R matches with ii (Extends primer on a DNA template).

S. Restriction endonuclease: Unlike exonucleases, endonucleases make cuts within the DNA molecule rather than at the ends. A restriction endonuclease identifies specific nucleotide sequences (called restriction sites) along the DNA double helix and cuts the sugar-phosphate backbone at precise locations. Therefore, S matches with iv (Cuts DNA at a specific position).

Combining all of our findings gives the correct matching sequence:
• P → iii
• Q → i
• R → ii
• S → iv
This corresponds exactly to the option: P-iii, Q-i, R-ii, S-iv.