In retroviruses, which statement describes how RNA is converted to DNA and what happens after integration?

• A. Reverse transcriptase converts RNA into DNA, and the DNA integrates into the host genome enabling persistent infection.
• B. DNA polymerase converts RNA into DNA, and the DNA remains episomal and non-integrated.
• C. Host RNA polymerase transcribes RNA into DNA, and there is no integration.
• D. RNA ligase converts RNA into DNA, and the DNA is degraded after replication.

Answer: (A)

Retroviruses carry reverse transcriptase to turn their RNA genome into DNA. That newly made DNA is then integrated into the host cell’s genome by the viral integrase enzyme, forming a provirus. Once integrated, this proviral DNA is replicated whenever the host cell divides and can be transcribed by the host’s RNA polymerase II to produce viral RNAs, supporting ongoing virus production. This integration is what allows persistent infection, because the viral DNA becomes a permanent part of the host genome and is maintained across cell generations.

Other statements don’t fit because they rely on enzymes or processes that don’t apply here: DNA polymerase doesn’t convert RNA to DNA; host RNA polymerase does not synthesize DNA from RNA; and RNA ligase does not convert RNA into DNA.