HIV, the virus that causes AIDS, has a genome made of RNA in…

HIV, the virus that causes AIDS, has a genome made of RNA instead of DNA. HIV contains an enzyme called reverse transcriptase that uses the RNA genome as a template to create a DNA copy of the viral genome after infecting a host cell. That DNA is then incorporated into the genome of the host cell, and the host cell machinery is used to make more HIV RNA and proteins. Cells that are not infected by HIV do not contain reverse transcriptase. The drug zidovudine, better known as AZT, is used to treat HIV infection. Although HIV multiplies by creating DNA copies, AZT doesn’t seem to affect other cells in the body that do DNA replication and divide but aren’t infected with HIV. Which hypothesis most likely explains this observation?