Viruses’ characteristics ? Acellular, have either DNA or RNA ? Causes infections of humans, animals, plants and bacteria. ? Cause most of the diseases that plague the world ? Cannot reproduce independently ? Have proteinaceous capsid around genome; some have an envelope around the capsid ? Do not divide or grow ? Neither grow nor respond to the environment ? Hijack the cell to make more viruses ? Have ultramicroscopic in size. ? They do not have organelles