An interesting look into the mind of Jonas Salk, essentially the father of modern vaccines.
"Biologists have discovered many ways in Nature of acquiring such information and of producing new combinations. For example, sexual reproduction, which results in new mixtures of inheritable information, may be seen as a producer of "mutations" in the sense implied above. "Mutations," as here defined, would also be produced by the introduction, either naturally or experimentally, of a virus into a sperm or egg cell, the genetic information of which would then be incorporated in either the DNA or the RNA and transmitted." -page 61
"Biologists have discovered many ways in Nature of acquiring such information and of producing new combinations. For example, sexual reproduction, which results in new mixtures of inheritable information, may be seen as a producer of "mutations" in the sense implied above. "Mutations," as here defined, would also be produced by the introduction, either naturally or experimentally, of a virus into a sperm or egg cell, the genetic information of which would then be incorporated in either the DNA or the RNA and transmitted." -page 61