fvvc

1. virology
Biol.3062
Cr. 2

2. 1.Introduction to Virology
Define virology?

3.  A virus is an obligate intracellular parasite containing genetic
material surrounded by protein
• Virus particles (virions) themselves do not grow or undergo
division.
• Viruses rely on host cells to provide the energy and materials
needed for replicating their genomes and synthesizing their
proteins.
• Most viruses are too small to be seen directly with a light
microscope.

4.  Viruses infect all types of organisms
 Animals
 Plants
 bacteria and archaea.
 Viruses are not really living.
 They are simply pieces of genetic code in a container that
chemically connect to a living cell, inject that genetic material
mechanically, and whose genes take over the cell's metabolic
processes.

5. Viral Genomes
 All cells contain double-stranded DNA genomes.
 Viruses have either DNA or RNA genomes.
 Virus genomes can be classified according to
 whether the nucleic acid in the virion is DNA or RNA
 whether the nucleic acid is single- or double-stranded, linear,
or circular.
 viruses whose genome consists of DNA follow the central
dogma of molecular biology (DNA→RNA→ protein)
 RNA viruses are exceptions to this rule

6. General characteristics of viruses
 Living characteristics of viruses
• Viruses belong to biology because they possess genes, replicate,
evolve, and are adapted to particular hosts, biotic habitats, and
ecological niches.
 Nonliving characteristics of viruses
• They are acellular
• They carry out no metabolism on their own and must replicate
using the host cell's metabolic machinery.
• viruses possess either DNA or RNA but not both.
• viruses contain only one type of nucleic acid
• They are totally dependent on a host cell for replication
• Viral components must assemble into complete viruses (virions)

7. Reasons for studying viruses
1.Some viruses cause disease
 Viruses are important agents of many human diseases, ranging
from the trivial (e.g. common colds) to the lethal (e.g. rabies),
 viruses also play roles in the development of several types of
cancer.
 As well as causing individuals to suffer, virus diseases can also
affect the well-being of societies.
 Smallpox had a great impact in the past and AIDS is having a
great impact today.

8. 2. Some viruses are useful
• Phage typing of bacteria :a phenotypic method uses
bacteriophages for detecting & identifying single strain of bacteria.
• Sources of enzymes: A number of enzymes used in molecular
biology are virus enzymes.
• Pesticides: Some insect pests are controlled with baculoviruses.
• Anti-bacterial agents: used to treat some bacterial infections of
humans.
3. Virus studies have contributed to knowledge
• Much of the basic knowledge of molecular biology, cell biology
and cancer has been derived from studies with viruses.

9. • Laboratory cultivation of viruses
 viruses lack metabolic machinery of their own and are totally
dependent on their host cell for replication, they cannot be
grown in synthetic culture media
 Animal viruses are normally grown in animals, embryonated
eggs, or in cell cultures where in animal host cells are grown
in a synthetic medium and the viruses are then grown in these
cells.
 Viruses are found wherever there is life
 The origin of viruses is unclear because they do not form
fossils
 They are on the borderline between life and non-life.