Final answer:
Oncogenic viruses introduce oncogenes or insert their genome near proto-oncogenes in host cells, leading to uncontrolled cell proliferation and tumor development. They can be either DNA or RNA viruses and are implicated in various forms of cancer. The process can occur via acute or slow viral-induced transformation.
Step-by-step explanation:
Oncogenic viruses have gained new genetic information in the form of oncogenes, which are expressed at higher than normal levels under the control of the stronger viral promoter. The resultant uncontrolled cellular proliferation can lead to the development of tumors. The process of oncogenesis can involve acute or slow transformation, depending on whether the virus carries an overactive oncogene (v-onc) or if the viral genome is inserted near a proto-oncogene within the host genome, respectively.
In acutely-transforming viruses, the presence of a viral-oncogene (v-onc) leads to immediate transformation upon expression. On the other hand, slowly-transforming viruses may have a longer latency period before tumor development, as the viral genome insertion needs to occur near a proto-oncogene and then lead to its overexpression.
Oncogenic viruses can be DNA or RNA viruses and are responsible for various types of cancers such as cervical cancer, liver cancer, T-cell leukemia, and lymphoma. These viruses alter the host cell cycle by either introducing oncogenes or interfering with tumor suppressor genes.