Question

1. Through what mechanisms do viruses evolve? Does a change to the nucleotide sequence necessarily confer a change to host integration, infection rate or transmissibility? Why or why not? 


Answer 1

There are varuious predictions about the evolution of viruses.Viruses are protien materials which are formed from

1. genetic material , RNA or DNA.

2. viruses are remnants of cellular organisms

3.viruses are evolved from their hosts.

Most supprting concept is the first one.

Two or more viruses can infect the cell at the same time ,they can swap and form a mixed viruse with unique properties. Genetic variation occurs by Recombination - mixing up and Random mutation - change in DNA or RNA sequence. Mixed segments are formed for example Human inflleunza + Bird influenza ----> Pig influenza virus formed.This leads to pandemic virus infection. eg: H1N1

High mutation rate occurs during copying of RNA or DNA.RNA virus have high mutation rate and cause severe symptoms may leads to death. DNA virus show low mutation rate and leads only drug resistance.Virus reproduce quickly ,high mutation rate and rapid life cycle.This effects the hosts based on the immune system. Fast evolution of viruse occurs due to large population and rapid life cycle.Virus protien are multifunctional, undergo unpredictable mutation and get altered by one or more interaction between virus and host.Environmental factors also influence viral multiplication such as temperatuer and humidityand their continous mutation make it difficult to predict the viral route of infection.