Has a dominant effect. Mutation in a nearby regulatory sequence that can alter gene expression or the quantity of gene product produced. A chromosome rearrangement that brings a DNA sequence from a distant site in the genome to close proximity of the gene and alter its expression. Both DNA and RNA tumor viruses, all alter the genome. RNA viruses, e.g., retroviruses.
Retroviruses can act as vectors for oncogenes and be tumor viruses.
They are RNA viruses, DNA is synthesized from RNA used as a template by RNA transcriptase, and then the DNA is inserted into the host genome. Rous sarcoma virus causes conncective tissue tumors known as sarcomas. They carry the src gene from the host. The viral src gene is an example of an oncogene and codes for a tyrosine kinase involved in the control of cell division. Oncogenes encoding products that affect apoptosis bcl-2, overexpression leads to suppression of apoptosis.