Virology-lecture-definition- viruses.pdf

Virus definition

1. What are the Viruses?
Biology Education
Spring Semester 2021
Lecturer: Sorankayfi
Virology
TISHK INTERNATIONAL UNIVERSITY
Faculty of Education
Biology Department
2020-2021
Lecture 1

2. Course objective
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This Virology course is aimed at advanced students to provide a contemporary understanding of how viruses
are built, how they infect and replicate in host cells, how they spread, evolve and cause disease, and how
infection of a host can be prevented.
This course will provide a balanced approach to Virology, combining the molecular and clinical aspects of
virology. While it is focused on human viruses, animal viruses, plant viruses and bacteriophages as well as
unusual virus-like agents (prions, viroids, etc.).

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Method Quantity Percentage (%)
Seminar 1 10
Participation 1 5
Quiz 3 5
Homework 1 5
Midterm Exam(s) 1 25
Final Exam 1 40
Total 100

4. Lecture Objectives
•A simple introduction to virology, and why virology.
•What is the virus?
•Viral usage.
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5. What is Virology?
•Virology is the bioscience of the study viral natures, in addition
to the basic relationships between viruses and theirhosts.
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Mimivirus
Genome length 1,181,549
500 nm

8. Why virology?
•Viruses infect all living things.
•We eat and breath billions of virus every day.
•We carry viral genome as our own genome!
•Viruses can be use as a crucial genetic engineering toll.
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20017

10. 10Tobacco mosaic virus
•Dmitri Ivanovskydiscovered virus in 1892
•The smallpox vaccine was the first vaccine to be developed against a contagious
disease In 1796
•Edward Jenner demonstrated that an infection with the relatively mild cowpox virus
conferred immunity against the deadly smallpox virus

11. Virus studies have contributed to knowledge
•A famous experiment carried by Alfred Hershey and Martha
Chase, and published in 1952, used phage T2 and E. coli to
provide strong evidence that genes are composed of DNA.
•The first enhancers to be characterized were in genes of simian
virus 40 (SV40).
•The first transcription factor to be characterized was the
transplantation (T) antigen of SV40.
•Introns were discovered during studies of adenovirus
transcription.
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12. Virus!
•Virusescanbedefinedas:Infectiousparticles,obligateintracellularparasites
comprisinggeneticmaterial(DNAorRNA)surroundedbyaproteincoat
and/oranenvelopederivedfromthehost.
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•More than 100 billion bacteriophage particle are at the
world’s water.
•The length of a head to tail line of 1030 phage is 100
million light years.

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Virome

14. Characters ofViruses
•Viruses are very small infectious agents (ranging from about 20 nm to about 300
nm indiameter).
•Contain only one kind of nucleic acid (RNA or DNA) as their genome neverboth.
•The nucleic acid is encased in a protein shell (capsid), which may be surrounded
by a lipid-containing membrane (enveloped) ornot.
•The entire infectious unit is termed avirion.
•Viruses are inert in the extracellular environment; they replicate only in living
cells, being parasites at the geneticlevel.
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15. •Virusesareobligateintracellularparasites,lackcellularorganellesandapparatus.
•Theviralnucleicacidcontainsinformationnecessaryforprogrammingtheinfectedhost
celltosynthesizevirus-specificmoleculesrequiredfortheproductionofviralprogeny.
•Virusesvarygreatlyinstructure,genomeorganizationandexpression,inadditionto
replication&transmissionstrategies.
•The host range for viruses may be broad or extremelylimited.
•Somevirusesareknowntoinfectunicellularorganismssuchasmycoplasmas,bacteria&
algae.Alsoallhigherplants&animals
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17. Benefits of Viruses
•Phage typing of bacteria.
•Sources of enzymes.
•Pesticides.
•Anti-bacterial agents.
•Anti cancer agent!
•Gene vector from protein production.
•Gene vector for treatment of genetic diseases.
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A schematic outline of the steps to generate transgenic chickens using viral vectors. ( A ) Suitable viral
expression constructs are developed and transfected into the appropriate packing cell line. ( B ) High-titer virus
is injected beneath the blastodermof the unincubatedegg. ( C ) Injected embryos are cultured for Ϸ 21 days
through hatching. ( D ) Founder (G 0 ) chicks are raised to sexual maturity. ( E ) Founder roosters positive for
the transgene in semen are mated with wild-type hens, and the G 1 offspring are screened for the presence of
the transgene (illustration by Jennifer Petitte).

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–Capsid:Theproteinshell,orcoatthatenclosesthenucleicacidgenome.
–Capsomeres:Morphologicunitsseenintheelectronmicroscopeonthesurface
ofthevirusparticles(representclustersofpolypeptides).
–Defectivevirus:Avirusparticlethatisfunctionallydeficientinsomeaspectof
replication.
–Envelope:Alipid-containingmembranethatsurroundssomevirusparticles
(capsid)(acquiredduringviralmaturationbyabuddingprocessthroughhostcell
membrane)
–Peplomers: Virus-encoded glycoproteins.
ImportantDefinitions

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–Nucleocapsid:Theprotein-nucleicacidcomplex(representingthepackaged
formoftheviralgenome).
–Structuralunits(Protomer):Thebasicproteinbuildingblocksofthecoat
whicharecollectionsofmorethanonenon-identicalproteinsubunit.
–Subunit :A single folded viral polypeptide chain.
–Virion:Thecompleteinfectiousviralparticle(servestotransfertheviral
nucleicacidfromonecelltoanother).

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