Question

1. Which of the following is a valid argument against including viruses in the group of ‘life’?

a) Viruses are very small

b) SomeviruseshavegeneticmaterialmadeofRNA,notDNA c) Viruses are not capable of independent reproduction

d) Virusesinfectawiderangeofhosts

e) Viruses can evolve very rapidly

2. M13 is a bacteriophage (a type of virus) that infects E. coli cells, and is capable of integrating into the host genome, becoming a prophage. It is likely to enter the ____________ when conditions are not conducive for rapid bacterial growth, which would cause the host cell to __________________.

a) lysogenic cycle : live b) lysogeniccycle:die c) lytic cycle : live

d) lyticcycle:die

3. You discover a drug which interferes with the ability of glycoproteins in the viral envelope (e.g., gp120) to interact with and bind to other biomolecules. Predict the most likely direct effect of this drug on 1) viruses that infect animal cells; and 2) viruses that infect bacterial cells (i.e., bacteriophage).

a) Animal virus: no effect; Bacteriophage: no effect

b) Animalvirus:preventedfrombuddingnewviruses; Bacteriophage: prevented from entering the lytic cycle

c) Animal virus: prevented from budding new viruses; Bacteriophage: no effect

d) Animalvirus:preventedfromadheringtoandinfectinghostcells; Bacteriophage: prevented from adhering to and infecting host cells

e) Animal virus: prevented from adhering to and infecting host cells; Bacteriophage: no effect

Answer 1

1. Option E is correct
Evolution and metabolism are characteristic features of living systems.
Viruses are non-living outside the host cell. They exhibit metabolism only in living cells. Hence they are considered as connecting links between living and non-living objects.

2. Option D is correct
Under unfavorable conditions, a bacteriophage enters the LYTIC CYCLE which leads to the DEATH of the host cell (Lysis)

3. Option D is correct
If the drug interferes with the interaction of the pathogen with the host cell receptor, it would lead to inhibition of infection.
Glycoprotein receptors are found in both animal and bacterial cells.