Question

There is a restriction endonuclease called EcoRI. What does Co part in it stands for?
A. Coli
B. Colon
C. Coelom
D. Coenzyme

Answer 1

Hint: The restriction endonuclease is also called molecular scissors as it cuts the DNA into discrete reproduced fragments. It is one of the crucial enzymes in recombinant DNA technology. EcoRI restriction endonuclease enzyme is derived from gram negative bacteria.

Complete answer:
 A restriction endonuclease is an enzyme which is derived from bacteria which can cut double stranded DNA into fragments. It does so by recognizing specific nucleotide sequences known as recognition or restriction sites. The term restriction means which obstructs the coming of foreign DNA in bacteria. These enzymes are basically found in bacteria and archaea and provide defence mechanisms against invading viruses. The name of restriction enzymes is based on the source and sequence number of production with the name of laboratories where they have been produced. The enzyme restriction endonuclease EcoRI is found in the bacteria E coli. So here the co stands for coli. The nomenclature of restriction enzymes says the first letter will be the genus name of bacteria, then the first two letters are of species, next is the strain of organism and Roman number tells the discovery order. So the enzyme EcoRI is isolated from bacteria Escherichia coli, strain RY13(R) and was the first endonuclease isolated from E coli. It recognizes the nucleotide sequence of 5’-GAATTC-3’ and its complementary 3’-CTTAAG-5’ on double strands of DNA. After recognizing its target sequence it cleaves and gives sticky ends. The action of restriction enzymes is either blunt or staggered. Blunt ends take place when both ends of cut DNA contain base pairs whereas in sticky ends the two cuts of DNA do form base pairs. After the staggering cut the resulting DNA fragments have 5’ or 3’ overhangs. The recognition sequence of EcoRI is a palindromic sequence that reads the same on the two strands when the orientation is kept the same.

Hence, the correct answer is option (A).

Note: W. Arber was the first scientist who postulated about restriction enzymes. He found the fragmentation of bacteriophage’s DNA into tiny pieces when it was injected into the bacteria. In 1978 Werner Arber, Hamilton Smith and Nathans received the Nobel Prize in Medicine for developing the smaller names of restriction enzymes.