Viruses are acellular or non cellular particles that contains an inner core of genetic material DNA or RNA that is covered by a nongenetic protein "coat" called a capsid. The protein coat is made up of protein subunits called capsomeres. Together, the capsid and the nucleic acid core forms the nucleocapsid. The nucleocapsid may be either enveloped or naked. Plant viruses are generally naked but animal viruses may or may not possess envelop. Plant viruses generally enters in toto as they cannot penetrate the cuticle of the host cell, so the entire virus comes in contact of host cell. The enveloped viruses inject their own nucleic acid inside the host cell.