Target Exam

CUET

Subject

Biology

Chapter

Biotechnology -Principles and Processes

Question:

Which of the following statements is not correct for Restriction enzymes?

Options:

Exonuleases remove nucleotide from ends of the DNA

Endonucleases make cuts at specific positions within the DNA

Ligases join sticky ends of DNA together

The first restriction endonuclease was Hind II

Correct Answer:

Ligases join sticky ends of DNA together

Explanation:

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

Ligases join sticky ends of DNA together . This statement is not correct in relation to restriction enzymes specifically, as ligases are not restriction enzymes. Instead, DNA ligases are enzymes that join DNA fragments together, particularly at the sticky ends created by restriction enzymes.

Restriction enzymes:

The cutting of DNA at specific locations became possible with the discovery of the so-called ‘molecular scissors’– 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

The first restriction endonuclease–Hind II, whose functioning depended on a specific DNA nucleotide sequence was isolated and characterized five years later. It was found that Hind II always cut DNA molecules at a particular point by recognizing a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for Hind II.

Restriction endonucleases are specialized enzymes that recognize specific DNA sequences, known as restriction sites, and then cut the DNA at or near these sites. They act like molecular scissors and can make cuts at precise positions within the DNA molecule. This ability to cleave DNA at specific sites is essential for various genetic engineering techniques, as it allows scientists to isolate and manipulate specific DNA fragments for various purposes.