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


Acetylcholine, a well known neurotransmitter, plays a critical synaptic role in the initial formation of memory. Chemical blockage of the acetylcholine receptors makes it harder to

Determine the Concepts of Soil Fertility  The soil fertility evaluation can be assessed by having an idea of the amount of nutrient which will be required for the growth of pla

Q. Show the Error Detection and Editing Function? Error Detection and Editing Function: Consciousness helps us avoid acting solely through habit. It allows us to make novel res


What is Metachronal wave? Describe. During the coordination of the ciliary movement, bands, or groups of cilia, are at different stages of their beating pattern, and this creat

subject for botany assignment

Explain the term of measurement of height in veous pressure? Measurement of Height: Measurement of height of venous pressure is done from the sternal angle of Louis verticall

Types of Aortic Stenosis:  Obstruction to left ventricular outflow is commonly at the valvar level. Less commonly it is at the sub valvar or supra valvar level. Sub valvar ob