What is Viruses ? Important Points, Explanation

What is Viruses ?

Virus­es are micro­scop­ic oblig­a­tory intra­cel­lu­lar par­ti­cles that must infect and take over a host cell in order to pro­lif­er­ate. They can only be observed under an elec­tron microscope.

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What is Virus ?

Scientist involved in discovering of viruses are :

  • Two sci­en­tists Dim­itri lwanows­ki and Mar­t­i­nus Biejer­nick played a cru­cial role to dis­cov­er viruses. 
  • Loef­fler and Frosch were are able to dis­cov­er the first ani­mal virus.
  • Fred­er­ick Twort and D herelle dis­cov­ered bac­te­rio­phages (bac­te­ria eat­ing viruses).
  • Wen­dell Stan­ley for the first time crys­tal­lized virus (TMV).

The viruses are made up of only two components 

  1. Pro­tein (cap­sid)
  2. Nucle­ic acid (viral genome).

Some Important Points About Virus are:

Virus can­not sur­vive and mul­ti­ply out­side the host cell.

The viral genome is pro­tect­ed against chem­i­cal and phys­i­cal dam­age by the pro­tein coat of the virus par­ti­cle called cap­sid.

The cap­sid and the viral genome are togeth­er called the nucle­o­cap­sid.

The build­ing blocks of cap­sid are pro­tein sub­units calles cap­someres.

On the viral cap­sid, spe­cial cap­sid pro­tein called Spikes are present are bind­ing sites of the virus so that it can attach to spe­cif­ic recep­tors on the host cells.

These cap­someres are respon­si­ble for the three dif­fer­ent sym­me­try group of virus­es are: icosa­he­dral , heli­cal and com­plex symmetry.

In some virus­es with con­ven­tion­al icosa­he­dral or heli­cal struc­ture, the nucle­o­cap­sid is sur­round­ed by a flex­i­ble loose-fit­ting mem­brane made up of pro­teins and lipids which are acquired from the host cell dur­ing repli­ca­tion known as the viral enve­lope and such virus­es are called ani­mal of enveloped virus­es. Virus­es which do not have an enve­lope are called naked virus or non enveloped virus.

The viral nucle­ic acid are genome is made of either Deoxyri­bonu­cle­ic Acid (DNA) or Ribonu­cle­ic Acid (RNA).

Virus­es with DNA as their genet­ic mate­r­i­al are called DNA virus­es and virus­es with RNA as genet­ic mate­r­i­al are called RNA virus­es.

The DNA and RNA virus­es are fur­ther sub­groups in 7 classes.(Baltimore classification)

T- phages (T1 through T7; T stan­dard for type) are a spe­cif­ic class of large Com­plex bac­te­rio­phages with icosa­he­dral heads , dou­ble strand­ed DNA with the char­ac­ter­is­tic head and tail structure.

Tobac­co mosa­ic virus has a heli­cal sym­me­try with pos­i­tive sense(+) sin­gle-strand­ed RNA in the middle.

Virus­es are eco­nom­i­cal­ly impor­tant as they cause loss­es from dis­eases and play a major ben­e­fi­cial role in med­i­cine Research and diagnostics.

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