Question

Which of the following statements does not hold true for restriction enzyme?

• A. It recognizes a palindromic nucleotide sequence
• B. It is an endonuclease
• C. It is isolated from viruses
• D. It produces the same kind of sticky ends in different DNA molecules

Answer 1

The correct option is C It is isolated from viruses

The restriction enzymes are called 'molecular scissors' and are responsible for cutting DNA on specific sites. These are not found in viruses but found in bacteria.

There are of two kinds of restriction enzymes - exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA.

Special sequence in the DNA recognized by restriction enzymes is called palindromic nucleotide sequence. The restriction enzyme may produce the same kind of sticky ends in different DNA molecules or it may produce blunt end in different DNA molecules.