ORGANIZATION AND CHARACTERSTICS OF VIRUSES

BARKATULLAH UNIVERSITY BHOPAL

PRESENTED BY MUHAMMAD ASIF KANTH

SUBMITTED TO :- DEPARTMENT OF ZOOLOGY AND APPLIED AQUACULTURE

M.SC IV SEM

VIRUS is either DNA or RNA, that is protected by a protein coat called a CAPSID.

Viruses:A • are noncellular or Acellular infectious agentsVirology:• study of viruses

Virologists:• scientists who study viruses

VIRUS:

The concept of a virus as an organism challenges the way we define life:

* Viruses do not breathe.* Viruses do not metabolize.* Viruses do not grow.* However, they do reproduce.

ASIF KANTH

General features of VirusesViruses are infectious agents with both living

and nonliving characteristics. 1. Living characteristics of viruses a. They reproduce at a fantastic rate, but only

in living host cells. b. They can mutate.

…General features of Viruses2. Nonliving characteristics of viruses

They are acellular, that is, they contain no cytoplasm or cellular organelles.

They carry out no metabolism on their own and must replicate using the host cell's metabolic machinery.

GENERAL FEATURES OF VIRUSES

Virus particles contains either DNA or RNA (not both)

Nucleic Acid is surrounded or coated by a protein shell (capsid)

Some viruses possess a membrane-like envelope surrounding the particle

…General Properties of virusesConsists of 1 molecule of DNA or RNA

enclosed in coat of proteinMay have additional layersCannot reproduce independent of living

cells nor carry out cell division as procaryotes and eucaryotes do

An intact viral particle is called a virion.

Replication Phases

V - Release- Assembly of virus

DNA and protein coat into whole new viruses

- Leaving the cell

ASIF KANTH M.SC IV SEM

Phase I

Phase II

Phase IV Phase V

Phase III

I, II, III - Viruses enter cell- Attachment to cell

membrane- Penetration inside cell- Losing virus protein coat

IV - Replication- Tricks cell into

making more viral DNA

- Tricks cell into making viral protein coat

Viruses Can Help Cells, Too

- Since viruses can transport DNA and RNA into cells, scientists are exploring Gene Therapy

- In Gene Therapy, viral genetic material is replaced with new DNA

- In time, this could be used to cure genetic diseases. Currently we have no cure for these types of illnesses

DISEASE VIRUSESAIDS HIV

Wart Herpes Simplex Virus

Flu Influenza

Measles Morbillivirus .

Cancer Hepatitis B

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Examples of some viral diseases:

The Size and Morphology of Selected Viruses

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Generalized Structure of Viruses

Viral componentsNucleic acids

Capsid

Envelope

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…Generalized Structure of Viruses

The Structure of Viruses

Virion size range is ~10-400 nmAll virions contain a nucleocapsid which is

composed of nucleic acid (DNA or RNA) and a protein coat (capsid)

Some viruses consist only of a nucleocapsid, others have additional components

Envelopes virions having envelopes = enveloped

viruses virions lacking envelopes = naked viruses

VIRAL ENVELOPES• Many viruses that infect humans and

other animals are enveloped.• Envelopes form when viral glycoproteins

and oligosaccharides associate with the plasma membrane of the host cell.• All envelopes have a phospholipid

bilayer.

The End! And ReviewViruses are very simple: a shell containing

either DNA or RNA.They infect by hijacking cells’ machinery to

force them to make more viruses.Viruses are tiny, even compared to a cell.Some viruses may prove useful in gene

therapy as natural carriers of DNA that was specially designed to be good for a particular reason.