Question

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

• A. Exonucleases remove nucleotides from ends of the DNA.
• B. Endonucleases make cuts at specific positions within the DNA.
• C. Ligases join sticky ends of DNA together.
• D. The first restriction endonuclease was Hind II.

Answer 1

The Correct Option is D

The first discovered restriction enzyme was EcoRI, not Hind II. Exonucleases and endonucleases have different roles in DNA processing. Ligases join DNA fragments, especially during molecular cloning.

Answer 2

Restriction endonucleases are enzymes that cut DNA at specific sequences. They are also known as restriction enzymes.

• Statement (1): Exonucleases remove nucleotides from the ends of the DNA. This is true. Exonucleases degrade DNA by removing nucleotides from the ends of the strand.
• Statement (2): Endonucleases make cuts at specific positions within the DNA. This is true. Endonucleases, including restriction enzymes, cut DNA at specific internal sites within the sequence.
• Statement (3): Ligases join sticky ends of DNA together. This is true. DNA ligase is an enzyme that joins DNA fragments, including those with sticky ends, by forming phosphodiester bonds.
• Statement (4): The first restriction endonuclease was not Hind II. The first restriction enzyme discovered was EcoRI, which comes from Escherichia coli. Hind II is one of the many restriction enzymes discovered later.