Question

Which of the following is an example of chemical scissors?
A. EcoRI
B. HindIII
C. BamHI
D. All of the above

Answer 1

Hint: The group of bacterial enzymes that can cut/split DNA at specific sites is known as restriction endonuclease, also known as the chemical scissors. They were first discovered in E. coli restricting the replication of bacteriophages by cutting the viral DNA (The host E. coli is protected from cleavage by the addition of methyl group., thus the enzyme restricting the viral replication are also known as restriction endonuclease.

Complete answer:
EcoRI is obtained from Escherichia coli and cut the DNA at a sequence of (\[5'\])AATTC($3'$), HindIII is obtained from Haemophilus influenzae and cut the DNA at a sequence ($5'$)AGCTT($3'$) and BamHI is obtained from the Bacillus amyloliquefaciens bacteria and the cut the DNA at a sequence ($5'$ )GATCC($3'$). The sequence at which the restriction endonuclease is cut consists of $4 - 6$bp and is known as the Recognition sequence. As the three above-mentioned enzymes can cut the DNA.
 hence option D is correct.

Additional Information:
EcoRI can cut the DNA and falls under the category of type I restriction endonuclease but the other two mentioned enzymes are also restriction endonuclease.
hence only option A is incorrect.

Type IiI restriction endonuclease has two subunits (for recognition and cleavage), cleavage site $24 - 26$bp from the recognition sequence. HindIII falls under the category of type III restriction endonuclease but the other two mentioned enzymes are also restriction endonuclease,
hence only option B is incorrect.

BamHI falls under the category of type I restriction endonuclease but the other two enzymes are also endonuclease, hence only option C is incorrect.

Note:
Type I restriction endonucleases are single enzymes with $3$ subunits (for recognition, cleavage, and methylation) cleaving up to $1000$ bp from the recognition sequence. Type II restriction endonuclease contains two enzymes (modify or cleave the recognition sequence), the cleaving site is the same or close to the recognition site.