General Virology and DNA Viruses
Which of the following statements best applies to the oncogenes of DNA viruses?
|A||They are early genes that perform essential viral functions|
|B||They are cell genes that are expressed during embryonic development|
|C||They encode a protein that has tyrosine kinase-like activity|
|D||They are virtually identical identical to the oncogenes of RNA tumor viruses|
a. DNA tumor viruses encode viral oncoproteins that are important to viral replication but also affect cel¬lular growth control pathways.
b. Most RNA tumor viruses belong to the retro¬virus family, carrying a reverse transcriptase enzyme (RNA-dependent DNA polymerase) that is responsible for contructing a DNA copy of the viral RNA genome.
c. Direct-transforming RNA oncoviruses carry an oncogene of cellu¬lar origin, whereas weakly oncogenic RNA viruses have no oncogene and produce leukemias after long incubation periods by indirect mechanisms.