1. Viruses are much smaller than bacteria, lack cellular structures, and can only replicate inside living cells. They contain either DNA or RNA surrounded by a protein coat and sometimes an envelope.
2. Viruses are classified based on their nucleic acid, protein coat, and genome organization/sequence. Examples include the herpesvirus family and human herpesvirus 2 genus.
3. Viral growth is measured in plaque-forming units and viruses can be cultured using cell cultures or embryonic eggs.
Viral classification and Types of Replication in virus Rakshith K, DVM
Precise presentation on Viral classification and Types of replication in Virus.
Entry of virus
Spread of virus
General steps in a virus replication cycle
Attachment, Penetration, Uncoating, Multiplication
Multiplication of Single-Stranded RNA (ss RNA) Viruses
Multiplication of Double-Stranded RNA (ds RNA) Viruses
Multiplication of Single-Stranded DNA (ss DNA) Viruses
Multiplication of Double-Stranded DNA (ds DNA) Viruses
Release of new virions
Common viral diseases of Bovines
VIRUSES CLASSIFICATION , LIFE CYCLE OF VIRUSES. CHARACTERISTICS OF VIRUSES Shylesh M
VIRUSES
LIFE CYCLE OF BACTERIOPHAGES
The word virus is derived from Latin word venom which means poisonous fluid that causes infection.
The branch of science that deals with the study of viruses is called Virology. It is the branch of Microbiology.
They show living characters inside the host and non living characters outside the host.
They contain either DNA or RNA as genetic material.
They have different size and shape. They cause diseases in plants, animals and micro-organisms .
Not cellular
Cannot carry on metabolic activities independently.
Contain either DNA or RNA, not both ( true cells contain both ).
Lack ribosomes and enzymes necessary for protein synthesis.
Reproduce only within cells they infect.
CLASSIFICATION OF VIRUSES
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
Based on the viral envelope
Named after David Baltimore, a noble prize winning biologist n 1971.
1. dsDNA viruses Eg: Adenoviruses, Herpiviruses.
2. ssDNA viruses Eg: Paravoviruses.
3. dsRNA viruses Eg: Reoviruses.
4. (+)ssRNA viruses Eg: Picornaviruses.
5. (-)ssRNA viruses Eg: Orthomyxoviruses.
6. ssRNA-RT viruses Eg: Retroviruses.
7. dsDNA-RT viruses Eg: Hepadnaviruses.
Tobacco mosaic:
Causative agent: Tobacco mosaic virus (TMV)
Symptoms: The leaves of infected plants develop mosaic patches ,it is due to destruction of chlorophyll or due to production of abnormal chlorophyll .blisters appear in the region of dark green spots these may be regular or irregular in advanced stages leaves curl and get distorted.
Adsorption of the virion to the bacterial cell.
Penetration and decoating of the nucleic acid .
Protein synthesis.
Breakdown of bacterial DNA.
Arrest of host cell development.
Replication of phage DNA.
Maturation of infective progeny.
Lysis and release of newly formed phages.
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
Viral classification and Types of Replication in virus Rakshith K, DVM
Precise presentation on Viral classification and Types of replication in Virus.
Entry of virus
Spread of virus
General steps in a virus replication cycle
Attachment, Penetration, Uncoating, Multiplication
Multiplication of Single-Stranded RNA (ss RNA) Viruses
Multiplication of Double-Stranded RNA (ds RNA) Viruses
Multiplication of Single-Stranded DNA (ss DNA) Viruses
Multiplication of Double-Stranded DNA (ds DNA) Viruses
Release of new virions
Common viral diseases of Bovines
VIRUSES CLASSIFICATION , LIFE CYCLE OF VIRUSES. CHARACTERISTICS OF VIRUSES Shylesh M
VIRUSES
LIFE CYCLE OF BACTERIOPHAGES
The word virus is derived from Latin word venom which means poisonous fluid that causes infection.
The branch of science that deals with the study of viruses is called Virology. It is the branch of Microbiology.
They show living characters inside the host and non living characters outside the host.
They contain either DNA or RNA as genetic material.
They have different size and shape. They cause diseases in plants, animals and micro-organisms .
Not cellular
Cannot carry on metabolic activities independently.
Contain either DNA or RNA, not both ( true cells contain both ).
Lack ribosomes and enzymes necessary for protein synthesis.
Reproduce only within cells they infect.
CLASSIFICATION OF VIRUSES
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
Based on the viral envelope
Named after David Baltimore, a noble prize winning biologist n 1971.
1. dsDNA viruses Eg: Adenoviruses, Herpiviruses.
2. ssDNA viruses Eg: Paravoviruses.
3. dsRNA viruses Eg: Reoviruses.
4. (+)ssRNA viruses Eg: Picornaviruses.
5. (-)ssRNA viruses Eg: Orthomyxoviruses.
6. ssRNA-RT viruses Eg: Retroviruses.
7. dsDNA-RT viruses Eg: Hepadnaviruses.
Tobacco mosaic:
Causative agent: Tobacco mosaic virus (TMV)
Symptoms: The leaves of infected plants develop mosaic patches ,it is due to destruction of chlorophyll or due to production of abnormal chlorophyll .blisters appear in the region of dark green spots these may be regular or irregular in advanced stages leaves curl and get distorted.
Adsorption of the virion to the bacterial cell.
Penetration and decoating of the nucleic acid .
Protein synthesis.
Breakdown of bacterial DNA.
Arrest of host cell development.
Replication of phage DNA.
Maturation of infective progeny.
Lysis and release of newly formed phages.
Holmes, in 1948, proposed a simple system of classifying viruses based on the type of cell (host) they infect:
Phytophagineae: They infect plants and they RNA as their genetic material. Eg: TMV,CaMV.
Zoophagineae: They infect animals and they have mostly DNA as their genetic material. Eg: Polio virus.
Pagineae: They infect bacterial cells, called bacteriophages they usually have DNA as genetic material.
DNA viruses and disease is a very important topic for pg entrance.....all important topics and questions have been discussed in detail....do make use of it......
Introduction, importance and general characters of fungi, bacteria, fastidiou...Pankaj Thakur
I've prepared this wonderful eye catch presentation to explain you about these complex biology not in bulk but in points the points which holds power...
General Characters and Classification of Viruses. Includes ICTV classification and Baltimore classification of viruses. A brief explanation of the Viral structure and Lifecycle.
0.1 What are viruses?
1. Origin of viruses
1.1 introduction
1.2 Theories
RNA molecules that existed before cells
cell components
micro-organisms.
1.3 Conclusion: How did viruses originate?
Concept of virology
Viruses
Types of viruses
Viral characteristics
Virion
Size and Shape
Structure
Replication
Viral Variation
Classification
Quiz
BEST OF LUCK
Replication of virus is very complicated process.
Virus never reproduce by division.
They are replicated by a process in which all components of virus are produced separately and are assembled into intact virion.
For replication of virus host is necessary.
Virus are host specific.
Host may be bacteria, plant ,animal.
DNA viruses and disease is a very important topic for pg entrance.....all important topics and questions have been discussed in detail....do make use of it......
Introduction, importance and general characters of fungi, bacteria, fastidiou...Pankaj Thakur
I've prepared this wonderful eye catch presentation to explain you about these complex biology not in bulk but in points the points which holds power...
General Characters and Classification of Viruses. Includes ICTV classification and Baltimore classification of viruses. A brief explanation of the Viral structure and Lifecycle.
0.1 What are viruses?
1. Origin of viruses
1.1 introduction
1.2 Theories
RNA molecules that existed before cells
cell components
micro-organisms.
1.3 Conclusion: How did viruses originate?
Concept of virology
Viruses
Types of viruses
Viral characteristics
Virion
Size and Shape
Structure
Replication
Viral Variation
Classification
Quiz
BEST OF LUCK
Replication of virus is very complicated process.
Virus never reproduce by division.
They are replicated by a process in which all components of virus are produced separately and are assembled into intact virion.
For replication of virus host is necessary.
Virus are host specific.
Host may be bacteria, plant ,animal.
Bacteriophage is the most common and extensively studied virus. The life cycle of bacteriophages. The transfer of their genetic system via the process of transduction (Generalised and Specialised) and studying the gene mapping in phages. This theoretical explanation about viruses and their genetic system will help the learner in the fields of biotechnology, microbiology, basic science, life science, and various other fields of biology.
Biology is a natural science concerned with the study of life and living organisms. Modern biology is a vast and eclectic field composed of many specialized disciplines that study the structure, function, growth, distribution, evolution, or other features of living organisms
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The term ‘virus’ derives from the Latin – poison or Venom.• Viruses are much smaller than bacteria, use their genome (DNA or RNA) to replicate themselves in the host cells and synthesize viral particle.The viral structure mainly having following parts: Viral genome, Capsid, Some are enclosed by an envelope while Some viruses have spikes.• Viruses are classified on basis of their morphology, structure, Genome, presence of envelope, type of host, mode of transmission, replication site and Baltimore classification.
1. Chapter 9
1. Differentiate a virus from a bacterium, with regard to
bacteria virus
size range Larger Smaller 20-1000 nm
Too small to be seen w naked eye
structural features Capsid, capsomere, envelope, spikes,
DNA/RNA
host-dependence Needs a living host; inert outside a host
mode of reproduction Binary fission Biosynthesis
2. List and briefly describe the key characteristics
of a typical virus.
● Contain a single type of nucleic acid, either DNA or RNA.
● Contain a protein coat (sometimes itself enclosed by an
envelope of lipids, proteins, and carbohydrates) that
surrounds the nucleic acid.
● Multiply inside living cells by using the synthesizing
machinery of the cell.
● Cause the synthesis of specialized structures that can
transfer the viral nucleic acid to other cells.
2. 3. Give an example each of viral family, genus, and strain
3. 4. List the criteria used in viral classification, with an example for each
Family: Herpesviridae
Genus: Simplexvirus, human herpesvirus 2
5. Name the unit used for measuring viral growth
(PFU) plaque-forming units
6. Briefly describe two methods routinely used for culturing viruses in the laboratory
1) In living animals
2) Embyonic eggs
3) Cell cultures
7. Briefly describe two methods for viral identification
Western Blotting
RFLP- restrictive fragment length polymorphism
4. 8. List all the stages of the lytic
(Fig.11) and the lysogenic (Fig. 12)
cycles of bacteriophage
multiplication, and describe the
key event in each stage
5. 8. List all the stages of the lytic
(Fig.11) and the lysogenic (Fig. 12)
cycles of bacteriophage
multiplication, and describe the
key event in each stage
6. 9. Briefly describe “phage conversion” and its effect on lysogenized host bacteria
The second result of lysogeny is phage conversion; that
is, the host cell may exhibit new properties. For example, the
bacterium Corynebacterium diphtheriae, which causes diphtheria,
is a pathogen whose disease-producing properties are related
to the synthesis of a toxin. The organism can produce toxin only
when it carries a lysogenic phage, because the prophage carries
the gene coding for the toxin. As another example, only streptococci
carrying a lysogenic phage are capable of causing toxic
shock syndrome. The toxin produced by Clostridium botulinum,
which causes botulism, is encoded by a prophage gene, as is the
Shiga toxin produced by pathogenic strains of E. coli.
7. 10. List all the stages in the multiplication of animal viruses, and describe the key event in each
stage
8. 11. Compare and contrast the events in bacteriophage and animal virus multiplication
(penetration) (entry)
9. 12. Differentiate the multiplication of enveloped and non-enveloped viruses
13. Differentiate the multiplication of (animal) DNA viruses and retroviruses
14. Define oncogenic viruses, with two examples
Viruses capable of inducing tumors in animals are called oncogenic viruses, or
oncoviruses
-papilloma viruses cause cervical cancer
-HBV Hepatitis B virus causes liver cancer
10. 15. Differentiate acute, latent and persistent viral infections, with one example of each
influenza
Shingles
TB
HIV
11. 16. Define “prion”, list its key characteristics, and give one
example each of prion diseases in
Animals: Mad cow disease (BSE)
and
Humans: Creutzfeldt-Jakob disease (CJD)
Stanley Prusiner proposed that infectious proteins caused a
neurological disease in sheep called scrapie. The infectivity of
scrapie-infected brain tissue is reduced by treatment with
proteases but not by treatment with radiation, suggesting that
the infectious agent is pure protein. Prusiner coined the name
prion for proteinaceous infectious particle.
12. 17. Define “viroid”, and give one example of an infection caused by a viroid.
Some plant diseases are caused by viroids, short pieces of
naked RNA, only 300 to 400 nucleotides long, with no protein
coat. The nucleotides are often internally paired, so the molecule
has a closed, folded, three-dimensional structure that presumably
helps protect it from attack by cellular enzymes. The
RNA does not code for any proteins. Thus far, viroids have been
conclusively identified as pathogens only of plants. Annually,
infections by viroids, such as potato spindle tuber viroid, result
in losses of millions of dollars from crop damage (Figure 13.23).