Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. When this occurs, it is possible for genes from bird flu virus and human flu virus to be combined, thereby producing a genetically distinctive virus, which can subsequently cause widespread disease.
The production of new types of flu virus in the manner described above is most similar to the phenomenon of
A) bottleneck effect.
B) founder effect.
C) natural selection.
D) gene flow.
E) sexual selection.
