A virus is an extremely small fragment of nuclei acid (DNA or RNA) surrounded by a protein coat. It is smaller than a living cell. Virus is not a cell. The study of viruses is called virology. Example of viruses
CHARACTERISTICS OF VIRUSES
i. They do not have a nucleus, cytoplasm or cell organelles.
ii. They have simple structures contain only one type of nucleic acid either DNA or RNA and not both.
iii. They are host specific. This means, a certain virus only attacks a specific host.
iv. When outside the host, they show no symptoms of life. They never grow, feed, excrete or respire while outside the host cell. they exist in a dormant state.
v. Most of viruses are infectious. They can cause diseases to their hosts.
vi. They cannot reproduce on their own. They must attack a host cell and use the materials in that cell to reproduce. This is called obligate parasitism.
Note: The ability of virus to reproduce inside the cell and crystallize in the absence of a living host places them between living and non-living things.
CHARACTERISTICS OF VIRUSES
i. They do not have a nucleus, cytoplasm or cell organelles.
ii. They have simple structures contain only one type of nucleic acid either DNA or RNA and not both.
iii. They are host specific. This means, a certain virus only attacks a specific host.
iv. When outside the host, they show no symptoms of life. They never grow, feed, excrete or respire while outside the host cell. they exist in a dormant state.
v. Most of viruses are infectious. They can cause diseases to their hosts.
vi. They cannot reproduce on their own. They must attack a host cell and use the materials in that cell to reproduce. This is called obligate parasitism.
Note: The ability of virus to reproduce inside the cell and crystallize in the absence of a living host places them between living and non-living things.