Introduction

Viruses

often cause serious diseases, relate to some cancers and congenital deformities, also can be used as tool for genetic engineering

Once infected, it is for life with harm

HIV, HSV-1, HCV

Once infected, it is for life but without harm if the vaccine is taken

Varicella, MMR

The vast majority of the viruses that infect us have little or no impact on our health or well-being. Why?

Because of our immune system

Virology

the study of viruses and virus-like agents, including, their taxonomy, diseases - producing properties, cultivation, and genetics

Obligate molecular parasites

viruses

Are Viruses alive

its is an organism with two phases. (virion and infected cell)

Viral size

Most are really small but recently pandoravirus was discovered to be around the same size as a bacteria

What virus can be seen under the light microscope

Pandoravirus

Viruses replicate by

assembly of pre-formed components into many particles

The evolving concept of virus

Discovered as early as 1728 and used to describe infectious diseases

Chamberland Filter

Developed a porcelain filter to remove bacteria from from drinking water but it didnt stop viruses only bacteria

Filterable viruses

the agent of tobacco mosaic disease passed through filters that retain bacteria

Why did most studies study tobacco mosaic disease

because of its economical value

1901

First human virus , yellow fever virus

1903

rabies virus

1906

variola virus

1908

chicken leukemina virus, poliovirus

1911

Rous sarcoma virus

1915

bacteriophages

1933

influenza virus

name used to depend on

the symptoms

The biological era (1898-1935)

• Mayer (infectious nature of tobacco mosaic)

• Beijerink (contagium vivum fluidum)

• Ivanovsky (TMV is filterable)

• Loeffler Frosch (Viruses as particulate matter )

• Holmes (local lesion aasay)

• Stanley (chemical purification of TMV)

The Biochemical era (1936-1981)

• Bawde, pirie (TMV is a ribonucleoprotein )

• Kausche, Pfankuch, Ruska ( First electron micrographs of viruses )

• Franklin, caspar (Structure of TMV particles )

• Hershey, Chase ( DNA is the genetic materisl of Phage T2)

• Fraenkel-Conrat williams; Gierer Schramm (RNA is the genetic material of TMV)

• Anderer et al., Tsugita et al. (Amino acid sequence of the TMV coat protein)

The molecular era (1982-2005)

• Sanger et al. (first viral genome sequence)

• Racaniello, Baltimore (infectious cDNA clone of poliovirus)

• Ahquist et al. (Infectious cDNA clone of BMV)

• Powell-Abel et al. (Transgenic plants expressing TMV coat protein have a delay in disease development )

• Dawson et al. (Infectious cDNA clone of TMV)

• Fire et al. ( dsRNA triggers RNA)

• Lindbo et al. (RNA-mediated resistance to plant virus in transgenic plants

The metagenomic era (2006-present)

• Metagenomics expands the known virosphere

• Tara Oceans (virus diversity at global scale )

• Roux et al. (Minimum information about uncultivated virus genomes)

Viruses are classified into different taxonomic group based on

1. The host

2. Capsid

3. Mode of reproduction

4. Nature of diseases caused

5. Genetic Material

6. Number of strands

7. Enveloped

On the basis of hosts

1. Animal virus

2. Plant virus

3. Bacteria virus

Animal virus

live inside animal cells. example smallpox, influenza, etc.

Plant virus

present inside plant cells . example TMV

On the basis of genetic material

1. DNA virus

2. RNA virus

3. DNA-RNA virus

DNA virus

Double stranded and single stranded DNA . example ; Bacteriophages T2 , lambda, and herpes virus.

RNA virus

Single stranded and double stranded RNA. Example ; Tumor virus and rice dwarf virus, Retrovirus (ds) TMV and influenza (ss)

DNA-RNA viruses

alternatively DNA or RNA. Example ; Leukovirus

Why do plant Viruses effect different plant cells

due to the simple entire passage when the cell wall is broken

Baltimore classification

Classify based on the creation of mRNA

Describe the graph

A virus needs to complete all its growth before bursting out of the cell

whats the virus depicted is the art

Polio

Chamberland Filter

First EM of bacteriaophage, 1939