The transcription of viral DNA

UKMLA PLAB AMC USMLE Prometric MCQ
UKMLA PLAB AMC USMLE Prometric MCQ
Correct Answer: CExplanation:When a retrovirus infects a cell its RNA genome is converted into DNA by the viral enco ...
Correct Answer: C

Explanation:
When a retrovirus infects a cell its RNA genome is converted into DNA by the viral encoded RNA-dependent DNA polymerase (reverse transcriptase). The DNA then integrates into the genome of the host cell where it can remain being copied as the host genome is duplicated during the process of cellular division. Contained within the sequences at the ends of the retroviral genome are powerful transcriptional promoter sequences termed long terminal repeats (LTRs). The LTRs promote the transcription of the viral DNA leading to the production of new virus particles. At some frequency the integration process leads to rearrangement of the viral genome and the consequent incorporation of a portion of the host genome into the viral genome. This process is termed transduction. Occasionally this transduction process leads to the virus acquiring a gene from the host that is normally involved in cellular growth control. Because of the alteration of the host gene during the transduction process as well as the gene being transcribed at a higher rate due to its association with the retroviral LTRs the transduced gene confers a growth advantage to the infected cell. The end result of this process is unrestricted cellular proliferation leading to tumorigenesis. The transduced genes are termed oncogenes AMC MCQ
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