IMMUNOLOGY

Detailed explanation-1: -Reverse transcription and integration are the defining features of the Retroviridae; the common name “retrovirus” derives from the fact that these viruses use a virally encoded enzyme, reverse transcriptase (RT), to convert their RNA genomes into DNA.

Detailed explanation-2: -Reverse-transcribing viruses replicate using reverse transcription, a process for making DNA from RNA templates. Their genomes can be either RNA or DNA. Retroviruses are ssRNA viruses that replicate through a DNA intermediate, thus requiring a virus-encoded RNA-dependent DNA polymerase (reverse transcriptase).

Detailed explanation-3: -Reverse transcriptases have been identified in many organisms, including viruses, bacteria, animals, and plants. In these organisms, the general role of reverse transcriptase is to convert RNA sequences to cDNA sequences that are capable of inserting into different areas of the genome.

Detailed explanation-4: -The retrovirus genome is typically made up of three genes: the group-specific antigen gene (gag), the polymerase gene (pol), and the envelope gene (env). The pol gene encodes the three enzymes-protease, reverse transcriptase, and integrase-that catalyze the steps of retroviral infection.

Detailed explanation-5: -The virion particles of all retroviruses contain reverse transcriptase, a multifunctional enzyme required for the synthesis of a DNA copy of the viral RNA genome soon after entry into the infected cell. The enzyme is the target of the major antiviral drugs currently in use in the treatment of AIDS.