VIRUSESVIRUSESVIRUSESVIRUSES

By : Ani RamliBy : Ani Ramli

A. Viruses Characteristics:

1. Viruses have two phases of existence, in their host cells(can be called as organis-ms) and outside the host cells(viruses are not living).

2. Viruses cannot be included in one of the kingdom in classification system of the five kingdom.

3. All viruses have parasitic characteristic and are harmful for their host.

4. Viruses consist of nucleic acid and capsid. Viruses with their mature parts are called virions.

5. Each virion consists of a type nucleid acid(only DNA or RNA) and capsid.

6. The size of viruses is extremely small with the diameter of about 20-400 nm.

B. Structure of Viruses

C. Virus Reproduction

1. Lytic cycle of Bacteriophage:

Lytic.swf

Lytic.swf

A lytic cycle consists of 3 stages :

1. Adsorption and penetration stage2. Replication stage3. Lyses stage

Lysogenic cycle consist of 3 stages :

1. Adsorption and penetration stage2. Gene insertion stage3. Division stage

D. The role of viruses in life

1. The harmful Role of VirusesA. Several diseases caused by viruses : a. AIDS(Acquired Imunodeficiency Syndrome) b. Avian Influenza(AI) c. Hepatitis d. Polio e. SARS f. Campak g. Ebola etc

B. Some diseases on animals which are caused by viruses :

a. Rabies on dogs, cats and monkeys.

b. Foot and mouth disease on cows and buffalos. c. The disease of chicken pestilence (Tetelo). d. The disease of chicken gumboro (to destroy the immunity).

C. Some diseases of plant which are caused by viruses :

a. Tobacco Mozaic Virus(TMV) b. Dwarf disease on the rice plant (Tungro). c. Citrus Vein Phloem Degeneration (CVPD) d. Potato Yellow Dwarf Virus.

2. The Beneficial Role of Viruses : a. Viruses can make bacteria cell

to produce antitoksin. b. Pathogen bacteria(dangerous) after being field with profage are not dangerous anymore. c. Viruses can be used to produce vaccine.

E. The ways of Disease Transmission and Disease

Prevention a. Direct transmission from patient

to healthy people via direct contact or tools they use.

b. Transmission via digestive tract(foods and drinks)

c. Transmission via animal vectors.