Read the following paragraph carefully and answer the given questions.
In the year 1963 the two enzymes responsible for restricting the growth of bacteriophage in E. coli were isolated. The first restriction endonuclease - Hind II, whose functioning depended on a specific DNA nucleotide sequence was 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. Besides Hind II, today we know more than 900 restriction enzymes that have been isolated from over 230 strains of bacteria, each of which recognize different recognition sequences.
In EcoR I the letter 'R' is derived from the -
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Name of the strain
Option (1) Order in which the enzyme is isolated — Incorrect. The order is shown by the Roman number at the end, the “I” of EcoRI. It tells that this was the first enzyme isolated from that strain.
Option (2) Name of the strain — Correct. EcoRI comes from Escherichia coli RY 13. The “R” stands for this strain, a particular line of the bacterium.
Option (3) Genus of prokaryotic cell from which the enzyme is isolated — Incorrect. The genus gives only the first letter, “E”, from Escherichia.
Option (4) Species of the prokaryotic cell from which the enzyme is isolated — Incorrect. The species gives the next two letters, “co”, from coli.
Note: This passage is taken from NCERT as it is. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Restriction Enzymes – “… The convention for naming these enzymes is the first letter of the name comes from the genus and the second two letters come from the species of the prokaryotic cell from which they were isolated, e.g., EcoRI comes from Escherichia coli RY 13. In EcoRI, the letter ‘R’ is derived from the name of strain. Roman numbers following the names indicate the order in which the enzymes were isolated from that strain of bacteria.”