The restriction enzyme responsible for the cleavage of the following sequence is ________. 5'−G−T−C−↓G−A−C−3' 3'−C−A−G−↑C−T−G−5' (a) EcoRl (b) Hindll (c) BamHl (d) EcoRll
Hint: The cleavage shown in the question by the restriction endonuclease enzyme will lead to the formation of blunt ends. Several restriction enzymes make staggered cuts at or near their recognition sites, producing ends with a single-stranded overhang.
Complete answer: A restriction enzyme is a protein that recognizes a specific, nucleotide sequence and cuts the DNA only at that exclusively specific site, which is known as a restriction site. There is a great deal of variation in restriction sites even within a species. Although these variations do not have phenotypic expression beyond the base sequences themselves. Over more than 300 restriction enzymes have been isolated from several bacteria that produce these enzymes with the help of genetic engineering. The recognition site of BamHI is GGATCC and it cleaves the bond between Guanine and Guanine, resulting in sticky ends.
The recognition site of EcoRI is GAATTC and it cleaves the bond between Guanine and Adenine, resulting in sticky ends. The enzyme EcoRII recognizes the sequence CCWGG and cleaves the DNA at this single site. The recognition site for HindII is GTCGAC and this enzyme specifically cleaves the bond between Guanine and Cytosine leaving blunt ends. So, the correct option is ‘HindII’. Note: In live bacteria, restriction enzymes function to defend the cell against invading viral bacteriophages. They are also used in the insertion of genes into plasmid vectors during the elaborate process of gene cloning and protein production. Restriction enzymes can also be used extensively to distinguish gene alleles by specifically recognizing the single base changes in DNA.