Question

Distinguish between Exonucleases and Endonucleases.

Answer 1

Hint: Most endonucleases are nonspecific as well as between some nucleotides they will sever the phosphodiester bond. This is a special category of endonucleases termed endonucleases of restriction.

Complete Answer:
Nucleases are a class of enzymes in which nucleic acids like RNA and DNA are hydrolyzed. The phosphodiester backbone binding individual nucleotides in a polynucleotide is hydrolyzed. Based on their position and mechanism of action on the nucleic acid, there are two types of nucleases i.e Endonucleases and exonucleases.

Sl.No	Exonucleases	Endonucleases
1.	Exonucleases refer to nuclease enzymes that separates the nucleotides from the ends.	Endonucleases cut the phosphodiester bond present in the polynucleotide from the centre.
2.	The phosphodiester bonds found at the 3 'and 5' end of its polynucleotide chain are hydrolyzed.	Inside a polynucleotide chain, they hydrolyze the phosphodiester bonds existing.
3.	Endonuclease has a protective role in which certain pathogens may be blocked from entering.	There are no protective properties of exonuclease against the invasion of pathogenic microbes.
4.	Instead of ending in oligonucleotides, exonucleases often cleave individual nucleosides at each end.	In the middle, the endonuclease cuts a DNA part, resulting in oligonucleotides.

Note: Endonucleases of type I are broad multi-subunit complexes which hydrolyze approximately 1000 base pairs at random sites. Smaller subunits which hydrolyze the sequences in the lack of ATP are type II endonucleases. Class III endonucleases which hydrolyze the 25 base pair sequences are also complicated.