Classification of viruses, Biology

Classification of Viruses

No evolutionary or phylogenetic exist between viruses. A   nature system of classification cannot, therefore, be devised for viruses.

Holmes (1948) proposed order vials for the viruses and divided it into three groups on basis of the category of hosts-

1.      Zoophaginae - Animal viruses

2.      Phytophaginae - Plant viruses and

3.      Phaginae - Viruses of bacteria blue green algae and fungi.

In 1962 Lwoff Horne and Tournier  decised a system of classifying viruses mainly on bases of nature of genome, capsid symmetry, number of structural  units capsomeres in the capsid size  of virions, etc. This system was largely adopted by the international committee on taxonomy of viruses (ICTV).

Under the LHT system, viruses are placed under a separate phylum, vira  vira  is division into two subphyla and each subphylum  is further divided into classes as follows-

Plant Viruses

These include bacteriophages, cyanophages  and mycophages. These are shaped like tadpoles or vertebrate sperms with a head and a tail. The genome, contained in the head, is usually double stranded DNA .A few spherical or filamentous phaages, possessing ss DNA or ds RNA ssRNA have also been discovered. Tailed phage's use their tails as hypodermic syringes for injecting their genome into their host cells through the rigid host cell wall.

In respect of host cell phage relationship there are two types of bacteria phage - virulent or tlytic and temperate or lysogenic , Lyrics  bacteriophages multiply  in  host bacterium which then undergoes complete  lyses' to release the resulting daughter phage's, In case of glycogenic bacteriophages, the viral genomes gets intergraded into bacterial genome and is, now called lysogeny, and the host bacterium is called  lysogenic. The prophase codes for new proteins which impart some new properties to the bacterium .This is called lyogenic or phage conversions. At times of binary fission, or any other stress condition, the prophases may separate from bacterial chromosome and become virulent. Lysogenic bacteriophages may, therefore , act as carriers of genes from one bacterium to others. This is called transduction.

Animals Viruses

About 600 or so known animals virus have been segregated into about one and a half dozen   families. Of these, the following families include the viruses of important human diseases.

Posted Date: 9/26/2012 6:00:27 AM | Location : United States







Related Discussions:- Classification of viruses, Assignment Help, Ask Question on Classification of viruses, Get Answer, Expert's Help, Classification of viruses Discussions

Write discussion on Classification of viruses
Your posts are moderated
Related Questions
Q. What are the main chemical compounds that destroy the ozone layer? The major chemical compounds that destroy the ozone layer are the CFCs, chlorofluorocarbons, or freons, su

Explain some Weight Loss during breastfeeding? Some women may want to return quickly to their pre-pregnancy weight. It is important to remember that some women will lose more,

Explain Brown fat and white adipose tissue - energy balance? There are two kinds of adipose tissue - Brown Fat is located around the shoulder blades and kidneys, constituting 1


Q. Use of Chemicals to Control and Destruct Microorganisms? Ans. The use of chemicals, as a process of food preservation, has been used since long, ever since man found

Removable soft tissue-borne partial dentures have one of the lowest patient acceptance rates in dentistry. Those patients wearing the partial dentures often exhibit greater mobilit

How Body size and composition affecting the BMR? Basal and resting energy expenditures are related to body size, being most closely correlated with the size of the fat-free mas

MISUSE OF BIOLOGY - Biological achievements are used against human race, e.g. 1 .       Bioweapons anitbiotic resistant infective micro-organism are used in wars. e.g., A

Tracheostomy Care A tracheostomy is an external opening made into the trachea in order to provide an artificial airway (an opening is made in the 2nd and 3rd or 4th trach

Temperature - Estuaries Another important variable is temperature. The temperature of estuary keeps on fluctuating it heats up and cools down more rapidly under prevailin