are enzymes that hydrolyze the phosphodiester bond in the backbone of nucleic
acids. These nuclease enzymes play an important role in degradation of old and broken
nucleic acids. There are two distinct types of nucleases: exonuclease and
endonuclease. Exonuclease are enzymes that cleave a terminal nucleotide off a
nucleic acid. Contrarily, endonuclease enzymes cleave a phosphodiester bond
within a nucleic acid. Furthermore, endonuclease enzymes can be specific or
nonspecific. Non-specific endonuclease cleaves at any internal bond or cleaves
a phosphodiester bond at 3' carbon. Likewise, a specific endonuclease cleaves
at a DNA sequence. Thus, endonucleases with extreme specificity are
called restriction enzymes

enzymes recognize a specific sequence of DNA, normally the sequence is between
four to six base-pair long. There are many different types of restriction
enzymes such as type I, II, and III. The article "Type II restriction
endonucleases—a historical perspective and more", introduces type II
restriction enzymes. Type II restriction enzymes mainly
occur in prokaryotes and are used to protect cells from viruses and other
infectious DNA molecules. Type II restriction enzymes include EcoRI and

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 EcoRV is a type II restriction enzyme derived
from Escherichia Coli. One concept that we did not
cover in class was the different forms of restriction enzymes. EcoRV is an
enzyme which cleaves at every 5' GATATC 3' DNA
sequence. The enzyme binds to DNA very loosely and scans for the 5' GATATC 3'
sequence, once the sequence is found, EcoRV kinks DNA at an angle and cleaves
at the 5' GATATC 3' sequence. EcoRV is the only form of restriction enzyme which
causes a conformational change to occur in the DNA.

one form of type II restriction enzyme that we have covered in class is EcoRI,
which is isolated from Escherichia Coli. The enzyme cleaves DNA at every 5' GTTAAC 3' DNA sequence. For instance, when DNA is
digested with RcoRI, it will cut DNA at every 5' GTTAAC 3' sequence. Essentially,
every person has a different TTAA sequence. Thus, everyone will have different
DNA fragments when digested with EcoRI. This form of DNA analysis is
fundamental in paternity testing and criminal investigation. As previously
established, we all have different TTAA fragments, thus during paternity
testing and criminal investigation you can easily identify who the
mother/father is of the child in question or who the criminal is when TTAA
fragments are compared.

discovery of nucleases has advanced molecular biology, genetics, and
biotechnology. Nucleases are classified as enzymes which help cleave a DNA
sequence. There are two fundamental forms of nucleases: exonuclease and
endonuclease. Restriction enzymes are a type of endonucleases. Inherently,
there are different types of restriction enzymes. Two most important type II
restriction enzymes are classified as EcoRI and EcoRV. Type II restriction
enzymes are primarily used to protect cells from viruses and other infectious
molecules. Additionally, EcoRI is used in DNA analysis during paternity testing
and criminal investigation. Therefore, the discovery of restriction enzymes
allows genes to be cloned, cleaved and overexpressed.