Question

Retroviruses have no DNA. However, the DNA of the infected host cell does possess viral DNA. How is it possible?

Answer 1

This process occurs through reverse transcription. A retrovirus possesses genetic material in the form of single-stranded RNA. One of its genes encodes reverse transcriptase, an enzyme located within the viral coat that synthesises a double-stranded DNA molecule from a single-stranded RNA template. Consequently, the transcription direction is the reverse of the standard pattern. Once the DNA complementary to viral RNA is produced, it follows normal biological rules to synthesise viral RNA and proteins. This newly synthesised DNA, which encodes viral proteins, becomes integrated into a chromosome of the host cell.