Learn about the viruses in biology, one of the least understood components of the living world. Here you will get information on the different kinds of viruses, their impact, and the viruses in biology.
VIRUSES
( DISCOVERY,CHARACTERISTICS,
MORPHOLOGY,DIESEASES)
DEFINITION:
The word virus Is derived from Latin word _venome_means poisonous substance or disease causing agent.
DISCOVERY:
50 years earlier from the development of the electron microscope, the existence of virus was demonstrated as a large group of acellular(without cell or non-celluar) disease causing agents composed of nucleic acid encapsulated in a protein coat.
L.PESTEUR (1884) , A.MAYERS (1886) During their study on tobacco mosaic disease concluded that the transmission of disease can b transfer from one host to another under controlled laboratory conditions, however the nature of the virus was not clear yet.
IN 1892 D.IWANOSKY Prepared an extract from tobacco plant that were suffering from mosaic disease, when this extractions was passed through a filter path to prevent the passage of bacteria the filtration was able to infect the healthy tobacco leaves so later on they named it as filterable virus.
IN 1898 M.BEIJERNICK established that viruses posses the property of replication that is common to all living things ,he further described that the these agents can multiply in the host cell.
F.TWORT AND F. d'Herelle independently discovered that some viruses infect bacteria, they termed these viruses bacteriophage virus.
IN 1935 W.STANLEY emphasized the structure of plant virus TMV, he crystallized the virus and then showed that they are largely composed of proteins, later other scientists showed that these Crystal's also contain a small but constant amount of RNA, further studies revealed that some virus contain DNA in addition to protein but no virus has found to have both DNA and RNA. In addition nuclei acid, some viruses contain lipids and some contain small amount of carbohydrates conjugated to their protein compounds. The largest and most complex virus , Poxviruses are composed of nucleic acid and several internal portions surrounded by membrane.
CHARACTERISTIC:
1- They are non-cellular parasitic.
2- They are disease causing substances
3- They are quite tiny therefore invisible in the light microscope and able to pass through filters that retain most bacteria.
4- They do not multiply in culture designed to support growth of bacteria ( they are non living outside the host cell).
5- They are composed of nucleic acid DNA and RNA core surrounded and protected by a protein coat called capsid.
6- The DNA and RNA functions as viral genome . Those that contain DNA contain an unusual biological property of having genetic information permanently encoded in RNA.
MORPHOLOGY OF
VIRUSES:
These ranges in size from 20 to 350 nm. Most viruses range in size between 10 to 100 nm. Since most viruses measure less than 150 nm, therefore they are visible only under electron microscope.
SHAPE:
The virus possessed a variety of shapes, the may be like rod liked i.e , elongated like a piece of insulated electrical cable (TMV), rounded (Mumps ,herpes, influenza viruses) tadpole shaped( bacteriophage) or bullet shaped ( rabies virus)
Bacteriophage exist in different shapes mostly exhibite a polyhedral head and a tail through which they infect the host cell .
CAPSID
CAPSOMERE
The virus coat (capsid) are often bulit up of identical repeating units called capsomeres ,the capsomeres form highly symmetrical structure that can be crystallized and help to study their structures through X_ray crystallography and electron microscopy.
VIRAL GENOME
The viral genome contists of nucleic acid .
VIRAL
INFECTION OF HUMAN BEINGS:
POLIO:
it is caused by polio virus and occurs mostly in childhood .
COLDS:
mostly colds are caused by rhinovirus,infection of upper respiratory tract.And shows symptoms of sore throat body aches fever.
RETEROVIRUSES:
The most famous virus of this group is HIV which causes Aids.Transmitts by physical contects or by blood treasmission.
(Influenza definition) FLU VIRUS:
They are minus strand enveloped RNA viruses, it might occur in epidemic form.It infects nose and throat.(Cough Flu And Fever)
RABIES:
The disease is caused by rhabdo virus. Due to dogs,bit and can be treated by anti rabies vaccine for dogs.
MEASLES AND MUMPS:
paramyoxyvirus cause measles and MUMPS, measles and mumps is one of the commonest diseases of childhood.So mmr injection and vaccine mmr should be taken for the cure.
HEPATITIS:
it is usually caused by virus ,and there is symptoms of fatty liver,liver cancer and other liver disease ,symptoms are yellow fever ,abdominal pain,enlargement, fatigue or sometimes fever.
Hepatitis A,Hepatitis B AND Hepatitis C These are the types of HEPATITIS virus.