Wednesday, April 28, 2010


Different types of nucleic acids present  in viruses
  ss DNA
ds DNA
 ss RNA
ds RNA

QX-174 bacteriophage
Many animal viruses.
T-even bacteriophages
Coli phages
Phyto phages--CMV,DMV
Many plant viruses TMV
Zoophages-polio virus, Influenza virus
Phyto phages-Wound tumour  virus,Maize rough dwarf virus,Rice dwarf virus
Zoo phages-Reo virus
Blue tongue virus


        Shape – Rod.                                                       Length – 300 nm
        Diameter – 18 or 19 nm                                      
        No. of capsomeres – 2,130                                  Symmetry – Helical
        Type of Nucleic acid – ss RNA                          Type of virus – Phytophage
        Diameter of central hole – 4nm/40A°                 No. of amino acids in a polypeptide chain – 158
        Length of m RNA involved in the synthesis of each capsomer of TMV – 1621.8A°
        No. of nucleotides present in the mRNA involved in the synthesis of each capsomer of TMV – 477
        No. of nucleotides in the RNA – 6500               Length of RNA – 22100 A°


Ø  Length of head – 65 nm                                
Ø  Breadth of head – 95 nm
Ø  Shape of head – Hexagonal                           
Ø  Shape of virus – Tad pole
Ø  Shape of tail – Rod                                        
Ø  Type of nucleic acid – ds DNA
Ø  Length of tail – 95 nm                                               
Ø  Diameter of tail core – 8 nm
Ø  No. of capsomeres in tail – 144                     
Ø  Capsomere rings in tail – 24
Ø  Shape of the tail plate – Hexagonal               
Ø  No. of capsomeres in each ring – 6
Ø  No. of appendages attached to the tail – 12  
Ø  Approximate length of bacteriophage – 160 nm
Ø  Approximate length of bacteriophage DNA – 1,60, 000 nm = 0.16 mm
Sequence of changes takes place during  lytic cycle
Collision between the virions and the bacterial cells- The phages get attached to the surface of the host at specific sites - Secretion of lysozyme - Formation of a hole in bacterial cell wall due to the action of lysozyme - Injection of phage DNA in to the host cell - Degradation of host DNA - Synthesis of coat proteins - Replication of phage DNA- Synthesis of different components of capsid - Assemblage of components and formation of complete virions - Host cell wall ruptures due to the action of lysozyme and the virisons are released.
Scientist Name
Alexander fleming
Anton van leeuwenhoek
Louis Pasteur and Robert koch
Earnest Haeckel

Christian Gram
Frederick Griffith
Lederberg and Tatum
Lederberg and Zinder
Heidi schulz
Edward Jenner
Louis Pasteur

Andre Lwoff


Pierie and Bawden

Gierrer and Schramm

Frankel and Conrat
Franklin et al
Felix ‘d’ Herelle
Discovered pencillin from a fungus penicillium notatum
Isolated an antibiotic from a bacterium Streptomyces griseus
Discovered bacteria, coined the term “Animal cules”.
Coined the term “Bacteria”.
Discovered the pathogenic nature of Bacteria.
Proposed three kingdom classification and placed bacteria under protista.
Proposed five kingdom classification, placed bacteria under monera.
Developed gram staining technique.
Discovered bacterial transformation in Streptococcus pneumoniae.
Discovered bacterial conjugation in E.coli
Discovered transduction Salmonella typhimurium
Discovered an ever largest bacterium Thiomargarita namibiensis
Developed vaccine for small pox
Developed vaccine for rabbies, coined the term virus, proposed germ theory of disease and established Pasteur research institute
Said that A virus is a virus, former director of Pasteur research
Discovered viruses.
Discribed viruses as “contagium vivum fluidum”.
Crystallized TMV.

Chemical analysis of viruses.
Discovered that the TMV is made up of nucleic acid and proteins.
Proved the nature of nucleic acid as infections agent and genetic material
Discovered that the genetic material in TMV is RNA
Described the structure of TMV
Discovered bacteria
Coined the term bacteriophage


Vein clearing
Vein banding

Ring spots

Breaking of flowers
Whitening or yellowing of entire leaf

Loss of chlorophyll in isolated patches

Loss of chlorophyll in the tissues close to veins
Loss of chlorophyll in the lamina except in areas of veins
Loss of chlorophyll in circular spots.

Reduced growth.
Abnormal growth
Loss of colour at certain parts and formation of dark colour at certain parts
Peach yellowing disease

Tobacco mosaic disease, Bean mosaic, Papaya mosaic , Cauliflower mosaic
Bhendi vein clearing
Citrus vein banding

Tomato spotted wilt, cherry ring spot, papaya ring spot
Rice stunting
Swollen shoot of cocoa
Tulip mosaic break


Transmitted viruses
Vegetative parts
Mechanical transmission
(Post fertilized form of ovule)
Pollen grains/Microspores
(First cell of male gametophyte)


Fungi(Olpidium brassicae)
(Heterotrophic thallophyte)
Phanerogamic parasites (Cuscuta)
(Complete stem parasite)
Potato virus, Sugar cane virus, Banana virus
Potato virus, TMV
Bean mosaic, Lettuce mosaic

Cherry ring spot virus

Rice tungro, potato leaf roll, papaya mosaic

Soil borne viral diseases

TNV, soil borne viral diseases.

Some viruses

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