Answer
The Rous sarcoma virus, discovered by Peyton Rous in 1911, holds a notable place in the history of virology. It stands as the first known oncogenic retrovirus, capable of inducing the formation of tumors in chickens. This groundbreaking discovery established a crucial link between viruses and cancer, pioneering the field of viral oncology and paving the way for significant advancements in understanding the molecular mechanisms underlying cancer development.