Online Counseling Resource
YCMOU ELearning Drive…
School of Architecture, Science and Technology
Yashwantrao Chavan Maharashtra
Open University, Nashik – 422222, India
SBT/SBI/SGS011-CP2-01
Introduction
Programmes and Courses
 SEP –SBT011 -U2-CP2
 SEP –SBT011 -U2-CP2
 SEP –SGS011 -U2-CP2
School of Science and Technology, Online Counseling Resource…
Credits
 Academic Inputs by
Sonali Alkari
Faculty YCMOU Nagpur Centre,
Faculty LAD college P.G. D of Biotechnology
Research officer Ankur Seeds Pvt Ltd
[email protected]
[email protected]
School of Science and Technology, Online Counseling Resource…
How to Use This Resource

Counselor at each study center should use this presentation to deliver
lecture of 40-60 minutes during Face-To-Face counseling.

Discussion about students difficulties or tutorial with assignments should
follow the lecture for about 40-60 minutes.

Handouts (with 6 slides on each A4 size page) of this presentation should
be provided to each student.

Each student should discuss on the discussion forum all the terms which
could not be understood. This will improve his writing skills and enhance
knowledge level about topics, which shall be immensely useful for end
exam.

Appear several times, for all the Self-Tests, available for this course.

Student can use handouts for last minutes preparation just before end
exam.
© 2007, YCMOU. All Rights Reserved.
4
School of Science and Technology, Online Counseling Resource…
Learning Objectives
After studying this module, you should be
able to:
 Describe viruses
 Discuss different types of viruses
 Explain structure of viruses
© 2007, YCMOU. All Rights Reserved.
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School of Science and Technology, Online Counseling Resource…
School of Science and Technology, Online Counseling Resource…
Introduction:1
The smallest organisms called as microorganisms or
microbes include the bacteria (prokaryotes), viruses,
fungi and protoctists.
 All these microorganisms are studied together for the
practical reasons because the techniques used in their
study are similar.
 The Russian botanist D.I. Ivanovasky [1985] prepared
an infectious extract from tobacco plant suffering from
mosaic disease.
 In 1898 Dutchman Beijerink coined the term “virus”
(Latin for poision) to such infectious extract obtained
from plant tissue.

School of Science and Technology, Online Counseling Resource…
Introduction:2
 Viruses are among the first biological structures to
be studied when electron microscope was developed
in 1930s.
 A virus (from the latin virus meaning "toxin" or
"poison"), is a sub-microscopic infectious agent
that is unable to grow or reproduce outside a host
cell.
 Each viral particle, or virion, consists of genetic
material, DNA or RNA, within a protective protein
coat called a Capsid.
 The capsid shape varies from simple helical and
icosahedral (polyhedral or near-spherical) forms, to
more complex structures with tails or an envelop.
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Introduction:3
 Viruses infect cellular life forms and are grouped into
animal, plant and bacterial types, according to the type
of host infected.
 Viruses often damage or kill the cells that they infect,
causing disease in infected organisms.
 A few viruses stimulate cells to grow uncontrollably and
produce cancers.
 Although many infectious diseases, such as the common
cold, are caused by viruses, there are no cures for these
illnesses.
 The difficulty in developing antiviral therapies stems
from the large number of variant viruses that can cause
the same disease, as well as the inability of drugs to
disable a virus without disabling healthy cells.
School of Science and Technology, Online Counseling Resource…
Characteristics :1
Viruse
have
the
following
characteristics.
 They are the smallest living
organisms
 They do not have a cellular
structure.
 They can only reproduce by
invading living cells.
 Therefore
they
are
all
parasitic.
 They
are
obligate
endoparasities, meaning that
they can only live parasitically
inside other cells.
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Characteristics :2
 They have a simple structure,
consisting of a small piece of
nucleic acid, either DNA or RNA,
surrounded by a protein or
lipoprotein.
 They are on the boundary
between what we regard as
living and non-living.
 Each type of virus will recognize
and infect only certain types of
cell.
 Viruses are highly specific to
their host.
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Viruses
Polio virus
T4 bacteriophage
Adenovirus,
The Polio virus, left, once crippled millions. Courtesy
of the MicrobeLibrary.org; © Jean-Yves Sgro, University
of Wisconsin.
The T4 bacteriophage, middle, is a virus that invades
bacterial cells. Courtesy of the MicrobeLibrary.org; ©
Dennis Kunkel.
Gold clusters bound to the knob protein of Adenovirus,
right. Courtesy of Brookhaven National Laboratory.
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Characteristics:3
 Viruses are the smallest living organisms,
ranging in size from about 20-300nm.
 They cannot be seen with the light microscope
and they pass through filters which retain
bacteria.
 On average they are about 50 times smaller
than bacteria.
 Often viruses reside in their host without
causing any disease or symptom. Such latent
viruses are undiscovered.
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Are Viruses Living?
 This question is often posed.
 If, to be defined as living, a structure must
possess genetic material(DNA or RNA), and be
capable of reproducing itself.
 It to be noted that viruses are not capable of
reproducing outside the host cell.
 It is suspected, though not proven, that viruses
are piece of genetic material that have ‘escaped’
from prokaryote and eukaryote cells and have
the potential to replicate themselves when they
go back into cell environment.
School of Science and Technology, Online Counseling Resource…
Types of Viruses
 All living things are susceptible to viral infections
... plants, animals, or bacteria can all be infected
by a virus specific for that type of organism.
 Depending upon the type of organism viruses are
classified as
 Human viruses: These are viruses which infect
only humans (for example, smallpox).
 Animals viruses: These are viruses which infect
only animals (for example, influenza),
 Plant virus: viruses which infect only a certain kind
of plant (for example, the tobacco mosaic virus).
 Bacteriophage: some viruses which infect only a
particular species of bacteria (for example, the
bacteriophage
which
infects
E.
coli).
School of Science and Technology, Online Counseling Resource…
Structure
 A virus particle, also
known as a virion, is
essentially a nucleic
acid (DNA or RNA)
enclosed in a protein
shell or coat.
 Viruses
are
extremely
small,
approximately 15 25 nanometers in
diameter.
Adenovirus - Images courtesy of
Linda M. Stannard, University of Cape
Town.
School of Science and Technology, Online Counseling Resource…
Genetic Material
 Viruses may have double-stranded DNA,
double-stranded RNA, single-stranded DNA or
single-stranded RNA.
 In different viruses, which of the four is the
"genetic material," depends on the nature and
function of the specific virus.
 The viral genome can consist of a very small
number of genes or up to hundreds of genes
depending on the type of virus.
 Note that the genome is typically organized
as a long molecule that is usually straight or
circular.
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Protein Coat
Papillomavirus
- polyhedral
capsid
 The protein coat that
envelopes the genetic
material is known as
a capsid.
 It can have several
shapes:
polyhedral,
rod or "complex."
 The protein subunits
of the capsid are
called capsomeres.
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Specialized Structures
 In addition to the protein coat, some
viruses have specialized structures.
 For example, the flu virus has a
membrane-like envelope around its
capsid.
 The envelope has both host cell and
viral components and assists the
virus
in
infecting
its
host.
Capsid additions are also found in
bacteriophages
 For example, bacteriophages can
have a protein "tail" attached to the
capsid that is used to infect the host
bacteria.
Influenza virus
Image courtesy
of Linda M.
Stannard,
University of
Cape Town.
Bacteriophage - Image
copyright Dennis Kunkel.
School of Science and Technology, Online Counseling Resource…
Bacteriophage:1
 Frederick Twort (1915) and Felix d'Herelle
(1917) were the first to recognize viruses
which infect bacteria, which d'Herelle called
bacteriophages (eaters of bacteria).
 In the 1930s and subsequent decades,
pioneering virologists such as Luria, Delbruck
and many others utilized these viruses as
model systems to investigate many aspects of
virology, including virus structure, genetics,
replication, etc.
 Some varieties of viruses attack only bacteria.
These types are called bacteriophages.
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Bacteriophage:2
 The bacteriophage lands
on the bacterium and
cuts a hole in the cell
wall with its 'injection
tube'. It then injects its
genetic material into the
bacterium.
 These
inserted
viral
genes take over the
bacterium's
genetic
machinery, and tell the
bacterium
to
begin
making new virus parts.
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Bacteriophage:3
 These parts come
together to make
whole
new
viruses inside the
bacterium. Then
the
bacterium
bursts open and
dies, releasing all
those
new
viruses to infect
more cells.
School of Science and Technology, Online Counseling Resource…
Plant Viruses
 Plant viruses attack
only plants.
 They are harmless to
all other organisms.
Yellow vein-banding symptoms on
grapevine caused by Grapevine fanleaf
virus.
 Prevention is the
only
economic
control
for
virus
diseases.
 Viruses consist of a
nucleic acid core and
a protein coat
School of Science and Technology, Online Counseling Resource…
Common Properties of Plant Viruses :1
 Plant viruses usually multiply only within living plant
cells, but some may be able to multiply within the
bodies of aphids and nematodes.
 A given plant virus may be able to multiply only within
the living cells of one species or genera of plants, but
some can multiply within the cells of a wide group of
plant families.
 In general, most organisms harbor both virluent and
and latent viruses.
 Temperate viruses embedd them selves within the
hosts nucleic acid and are transmitted generation to
generation just like genes of the host.
School of Science and Technology, Online Counseling Resource…
Common Properties of Plant Viruses:2
 Plant viruses usually multiply
only within living plant cells,
but some may be able to
multiply within the bodies of
aphids and nematodes.
 A given plant virus may be
able to multiply only within
the living cells of one species
or genera of plants, but
some can multiply within the
cells of a wide group of plant
families.
Tobacco Mosaic Virus
School of Science and Technology, Online Counseling Resource…
Animal Viruses
 Animal viruses are intracellular
parasites that reproduce only after
the host animal cell.
 There are several types of animal
They are commonly grouped into
according to the type of genetic
present in the virus.




Double-Stranded DNA
Single-Stranded DNA
Double-Stranded RNA
Single-Stranded RNA
obligate
invading
viruses.
families
material
School of Science and Technology, Online Counseling Resource…
DNA-containing Viruses
Herpes viruses are found in a
wide range of hosts; at least
seven different species are known
to
infect
humans,
including
herpes simplex. Genital herpes
has no cure.
Hepatitis B
Hepatitis B virus causes both acute and
chronic liver infections in humans. An
unusual feature of these infections are
the length of time they last; up to
Papillomavirus
several months in acute infections, and
many years (or for life) in chronic
infections
The adenovirus consists of a slender
Adenovirus
shaft with a globular head. Adenoviruses
can infect humans, and can cause
respiratory illness or conjunctivitis ('pink
eye').
Herpes Virus
The
papillomavirus
attacks human
cells, and can
cause ordinary
warts,
which
are harmless.
But
some
varieties cause
genital warts;
these tumours
can
become
malignant
School of Science and Technology, Online Counseling Resource…
RNA-containing Viruses
Influenza
 The influenza virus causes
acute
upper
respiratory
disease in humans, usually
accompanied by a fever.
 These viruses are roughly
spherical,
and
about
200
millionths of a millimetre in
diameter .
Enterovirus
 Enteroviruses belong to one of
the largest families of viruses;
others in this family include
rhinoviruses (which cause the
common cold), cardioviruses,
apthoviruses and hepatoviruses
(which cause hepatitis A).
 Enteroviruses
usually
reproduce in the intestine. An
important enterovirus is the one
which causes polio
School of Science and Technology, Online Counseling Resource…
What You Learn…
 You have learnt :
 Characteristics of viruses
 Structure of virus :genetic martial ,
protein coat
 Viruses are on the boundary line of living
and non-living.
 Types of Plant viruses
 Types of animal viruses
 Bacteriophages
School of Science and Technology, Online Counseling Resource…
Critical Thinking Questions
1. Describe in the detail the structure
of viruses .
2. Describe different types of viruses.
3. Write a short not on Bacteriophages
4. What is viruses? Give its different
properties.
© 2007, YCMOU. All Rights Reserved.
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School of Science and Technology, Online Counseling Resource…
Hints For Critical Thinking Question
1. genetic
material,
protein
coat,
specialized structures.
2. Animal, plant, Human, bacteriophages,
DNA/RNA containg
3. bacteria infecting viruses, structure.
4. Small particles, living/nonliving, self
replicating, requires living host for
multiplication.
© 2007, YCMOU. All Rights Reserved.
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School of Science and Technology, Online Counseling Resource…
Study Tips
 Book1
 Title:The Living World
 Author: George Johnson
 Book2
 Title: ABC Of Biology
 Publisher: Holy Faith
 Book3
 Title: Biological Science
 Author: Taylor, Green & Stout
School of Science and Technology, Online Counseling Resource…
Study Tips
www.en.wikipedia.org
Microsoft Encarta Encyclopedia
http://en.wikipedia.org/wiki/
Wikipedia the free encyclopedia
School of Science and Technology, Online Counseling Resource…
End of the Presentation
Thank You !