Final answer:
The presence of src gene allows retroviruses like Rous sarcoma virus to transform cells.
Step-by-step explanation:
The presence of src gene allows Rous sarcoma virus and other retroviruses to transform cells. Retroviruses, including Rous sarcoma virus, have an env gene that encodes for a protein envelope surrounding the retroviral DNA. This protein envelope helps the virus attach to the host cell. However, the presence of the env gene is not specifically related to the transformation of cells. The pol gene is responsible for encoding the reverse transcriptase and other enzymes needed for the replication of the retroviral DNA within the host cell. The LTRs (Long Terminal Repeats) are regulatory regions at the ends of the retroviral genome that control the transcription and replication of the viral genes.
The Rous sarcoma virus and other retroviruses have the unique ability to transform cells due to the presence of a gene known as the src gene. This src gene encodes an overactive oncogene that can induce the transformation of the infected cell upon expression. Unlike the LTRs, pol gene, or the env gene, the src gene directly contributes to the oncogenic capability of the virus, leading to uncontrolled cellular proliferation once it is activated within the host cell.