Chapter 25 - Bacteria, Archaea, and Viruses - 25.4 - Viruses Have Evolved Many Times - 25.4 Recap - Learning Outcomes - Page 549: 2

One viral origin theory is that some of the DNA viruses represent highly reduced parasitic organisms that have lost their cellular structure over the course of time, along with their ability to reproduce independently of another organism. Another theory is that double-stranded RNA viruses may have descended from single-stranded RNA ancestors.

One viral origin theory is that some of the DNA viruses represent highly reduced parasitic organisms that have lost their cellular structure over the course of time, along with their ability to reproduce independently of another organism. Another theory is that double-stranded RNA viruses may have descended from single-stranded RNA ancestors.