Question

In the nomenclature of enzyme restriction endonuclease, the roman numeral indicates
A. Number of times it is used
B. The order of discovery from source
C. Number of cuts of DNA
D. Number of recombinants formed

Answer 1

Hint: The first endonuclease restriction was isolated from S. pneumoniae which is a bloodstream infection caused by gram-negative pathogenic bacteria. Endonuclease restriction is an enzyme generally referred to as molecular scissors. DNA technology is an important tool in recombining.

Complete answer: An enzyme isolated from bacteria that can break dsDNA into fragments is a restriction endonuclease. It does so by identifying the 'recognition' or 'restriction site' of unique nucleotide sequences. The word 'restriction' comes from the discovery that these enzymes inhibit or impede the entry into the bacteria of foreign DNA. The name of endonuclease restriction contains abbreviations of the bacterial species from which the enzyme is extracted. Based on the organism from where they were discovered, restriction enzymes are named accordingly. The first three letters of the name are italicised since they abbreviate the name of the organism's genus and species. The fourth letter is from the name of the bacterial strain. To distinguish unique enzymes from bacteria possessing multiple restriction enzymes, Roman numerals are used. The naming convention for restriction enzyme is as follows:
a) The first letter comes from the genus and the second letter comes from the species of bacteria or prokaryotic cells that have been used to isolate the enzyme.
b) The following alphabet comes from the strain name.
c) The roman number shows the order of separation of enzymes from the bacterial strain.
Therefore, option B is the correct answer.

Note: The action of the restrictive enzyme is either blunt or phased cuts. Blunt ends occur when both ends of the DNA cut have a base pair. Since both DNA ends do not have a base pair in staggered cuts, instead, they have single nucleotides present, therefore, they are known as sticky ends. After the staggering cut, the resulting restriction DNA fragments contain 5' overhangs or 3' overhangs.