Question

Initial studies of the influenza A virus by Walter Fitch and colleagues showed that ________.

1) influenza A actually has DNA as its genetic material

2) selection is causing influenza A to become more virulent over time

3) selection by the immune system drives change in hemagglutinin's antigenic sites

4) protein evolution in influenza A is consistent with the neutral theory

5) flu strains from one host cannot exchange genetic material with strains from another

Answer 1

Walter Fitch's studies on influenza A virus showed that immune system selection results in changes to the antigenic sites of hemagglutinin. This occurs through antigenic drift and can contribute to the virus's ability to evade the immune response. Antigenic shift can lead to the emergence of highly virulent novel influenza strains.

Step-by-step explanation:

Initial studies of the influenza A virus by Walter Fitch and colleagues showed that selection by the immune system drives change in hemagglutinin's antigenic sites. This process is part of what is known as antigenic drift, where mutations in the genes for surface proteins such as neuraminidase and/or hemagglutinin result in gradual changes to these proteins, allowing the virus to evade the host's immune response. Another process known as antigenic shift involves the mixing of genes from two different influenza viruses infecting the same cell, resulting in a virus with a mixture of proteins from the original strains, potentially leading to highly virulent strains and pandemics when individuals lack an immune response to these novel viruses.