Question

Which among the following statement is incorrect?

• A. Hind Ⅱ was the first restriction endonuclease to be isolated and characterised
• B. The Roman number at the end of restriction enzymes indicates the strain number of the bacteria
• C. Endonuclease binds to the specific nucleotide sequence in the DNA and cuts the sugar-phosphate backbone
• D. Today more than 900 restriction enzymes have been isolated from over 230 strains of bacteria

Answer 1

The correct option is B The Roman number at the end of restriction enzymes indicates the strain number of the bacteria

Restriction endonuclease recognizes specific nucleotide sequences in a DNA molecule, often a palindrome known as restriction site, and cleaves the phosphodiester bond (sugar phosphate backbone) in both the DNA strands at a specific nucleotide within the restriction site.

Restriction endonucleases are naturally present in the bacteria where they provide protection against invading viral DNA. Hind II was the first restriction endonuclease to be isolated and characterised. Today more than 900 restriction enzymes have been isolated from over 230 strains of bacteria.

Restriction endonuclease nomenclature consist of four parts:

• The first letter in a restriction endonuclease indicates the genus of the bacteria it is isolated from.
• The second two letters indicate the species.
• If the fourth letter is present, it indicates the strain of the bacteria.
• The Roman number at the end represents the order in which that particular restriction endonuclease was isolated from that strain of bacteria.