Nucleases are ubiquitous phosphodiesterase enzymes that cleave phosphodiester bonds within nucleic acid molecules. They are indispensable for the both cellular and viral development. Nucleases that are specific for DNA are called deoxyribonucleases (DNases), while nucleases that recognize RNA (RNases) are called ribonucleases. There are many distinct types, all of which function to recognize a wide range of different yet types of molecules. Some nucleases, however, cleave nonspecific nucleic acid substrates. They also provide a variety of protective mechanisms. For example, they are responsible for degrading host cell DNA following viral infection and they are essential to DNA repair mechanisms such as nucleotide excision repair. Other important functions within the cell that nucleases play a role include DNA synthesis, DNA recombination, maturation of RNAs or RNA splicing, and DNA packaging involving either chromosomes or viral compartments. While some nucleases serve to degrade exposed single-stranded DNA, others are specific for...