Question

A highly virulent strain of a common and previously innocuous virus has been discovered and you have decided to conduct
a series of experiments to understand what has caused
this new strain of virus to be so virulent. Fortunately, the innocuous strain was known to have a small, linear double-stranded DNA genome with only a few genes. We find that the virulent strain has two new genes.

Innocuousstrain: Gene A Gene B GeneC

Virulent strain: Gene A Gene B gene C gene D gene E

Suppose that you conduct your experiments and you find that gene D is sufficient but it is NOT necessary for virulence.

- How might you explain such a result?

- And test that explanation?

Answer 1

Such a result might be explained by creating a loss of function(LOF) mutant form of gene D. Lof mutant is a condition where sample gene is deactivated partially or fully. Here we use a fully inactivated gene D and other genes kept as previous and if the strain is still showing virulence means gene D is not necessary.

Looking at the genes of virulent strain it may be possible that gene E is necessary for virulance. To prove this we could create a lof mutant of geneE and other genes as those were and if this strain is insufficient for virulance means gene E is necessary for virulence.