Question

Suppose you are a researcher in an influenza lab and your team has uncovered four strains that have evolved changes from last year’s influenza virus. Strain A has evolved four changes in its surface proteins and three changes in its interior proteins. Strain B has evolved two changes in its surface proteins and seven changes in its interior proteins. Strain C has evolved six changes in its surface proteins and none in its interior proteins. Strain D has evolved only a single change in its surface proteins and none in its interior proteins. Assuming that all other factors are equal, which strain is most likely to be infectious?

Strain A
	Strain B
	Strain C
	Strain D
	All of the strains are equally likely to be infectious.

Answer 1

Answer: Choice C (strain D)

Explanation: The virulence of a strain depends upon the nature of surface receptors it has and thus determining its identity the host system. The changes in interior protejns do not matter in determining the virulence. Here, it is important to note thag a single change in amino acid or surface protein is more likely to develop a new strain as compared to a number of changes since a single change is more capable of determining the specificity of the protein . Hence, strain D must be the virulent strain in this case.