Which of the following statements is not correct for Restriction enzy…

The correct answer is Option (3) → Ligases join sticky ends of DNA together.

Restriction enzymes are the ‘molecular scissors’ of genetic engineering. They cut DNA at specific recognition sequences.

Option (1) Exonucleases remove nucleotide from ends of the DNA. — Correct for restriction enzymes. Restriction enzymes belong to the class of enzymes called nucleases, which are of two kinds: exonucleases and endonucleases. The book describes restriction enzymes through these two kinds.

Option (2) Endonucleases make cuts at specific positions within the DNA. — Correct for restriction enzymes. Restriction enzymes are endonucleases. Each one cuts both strands of DNA at a specific palindromic sequence.

Option (3) Ligases join sticky ends of DNA together. — Not correct for restriction enzymes. The statement is true of DNA ligase, a different enzyme. Restriction enzymes cut DNA; ligases join the cut pieces. A ligase is not a restriction enzyme, so this statement does not describe restriction enzymes.

Option (4) The first restriction endonuclease was Hind II. — Correct for restriction enzymes. Hind II was the first restriction endonuclease isolated and studied. It always cuts DNA at a particular point by recognising a specific sequence of six base pairs.

NCERT Extract:
Restriction Enzymes – “… Restriction enzymes belong to a larger class of enzymes called nucleases. These are of two kinds; exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA.”
Restriction Enzymes – “… When cut by the same restriction enzyme, the resultant DNA fragments have the same kind of ‘sticky-ends’ and, these can be joined together (end-to-end) using DNA ligases (Figure 9.2).”