Question

(a)EcoRI is a restriction endonuclease. How is it named so? Explain
(b) Write the sequence of DNA bases that the enzyme recognises. Mention the point at which the enzyme makes a cut in the DNA segment.

Answer 1

Hint: EcoRI is a restriction endonuclease enzyme generated from species E. coli. The Eco portion of its name of enzyme derives from the species in which it was isolated, whereas the R, in this case RY13, represents the specific strain. The last part of its name, the I, suggests that it was the first enzyme in this strain to be isolated.

Complete answer:
(a) EcoRI is so called because it operates at particular locations on the inner surface of DNA and breaks it into fragments, while exonuclease works on the ends of strands and will not be used for the circular vector. EcoRI produces 4 sticky nucleotide ends with 5' ends and AATT overhangs.

(b) EcoRI is an endonuclease restriction enzyme isolated from E. Coli bacterium, which slices through the DNA of the palindromic sequence 5' GAATTC 3' and the opposite sequence on the other strand, 3' CTAAG 5' EcoRI 'breaks' into the series between the base of adenine and the base of glycine on each strand, leaving sticky ends. EcoRI as well as other restriction endonucleases are also used to split DNA into unique sequences before fragments are placed via gel electrophoresis and arranged by size, known as DNA restriction digests. EcoRI is an example of a restriction enzyme of type II. There has been evidence that this type of restriction enzymes is evolutionarily related.

Note: There are variations between codons used by E. Coli as well as codons that encode endonuclease for EcoRi and similarities between the EcoRI amino acid sequence and other restriction endonucleases, such as RsrI, thus suggesting the EcoRI gene in E. Coli may have been obtained through lateral gene transfer.