Animal Viruses
All animals in their lifetime will be infected by a virus, whether it’s a common influenze virus or a sexually transmitted virus such as HIV. Viruses are parasites that reproduce only after invading the host cell. They are not classified as living organisms as they lack some of the many traits wee associate with living, such as:
1) Breathing
2) Interaction
Plant Viruses
Plant viruses cause a large amount of damage to farm crops. Seeding and propagation of plants by farmers can pass on virus infections which leads to further widespread disease. Symptoms of plant virus infection@
Bacterial Viruses
Strange to believe, however bacteria can become infected and killed by viruses, these are called bacteriophages. These viruses were first discovered in 1915 and have been essential in molecular biology since. The properties of the bacteriophage allows insertion of modified genes into bacteria to express them.
Structure
A virus or virion is normally shown as a 3 dimensional shape, an outer coat of protein and a inner material of DNA or RNA. Virus particles are much smaller than bacteria; their average size is in the 10-30 nanometre range. The protein coat or capsid can take the form of many shapes; within this coat proteins are expressed which host cells immunesystems can detect if immunisation has been carried out. These protein genes can become mutated over generations producing viruses which the host is no longer immunised against. In other words the host cell can not recognise and exuberate an immune response because of failure to recognise a threat.
Genetic material
Viruses can either have DNA or RNA. DNA is double stranded nucleotides vs. RNA which is made of single nucleotide sequences. The genome of a virus is considered relatively simple compared with other organisms such as humans. The genome holds information that expresses the protein coat, to protect the genetic material from the environment as well as the complete gene sequence for attacking host cells.
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