1. Retroviruses are enveloped viruses. The virion carries two copies of single-stranded RNA plus enzyme, reverse transcriptase.
2. When the viruses enter the cell, the single stranded RNA and reverse transcriptase are released inside the cell.
3. The single-stranded RNA (function: viral information) is converted to double stranded DNA by the enzyme reverse transcriptase (function: transcribe ssRNA to cDNA)
4. The double stranded DNA is integrated into the host cell’s chromosomes as a provirus
5. Some cells carry provirus in the latent state and no virions are produced whereas other infected cells continuously synthesize new virions. The viral DNA is transcribed to produce one long polygenic messenger RNA.
6. The messenger RNA is translated onto a long polyprotein, which is then cleaved by a viral-encoded protease to yield the individual proteins that make up the virons.
(McGraw-Hill. Replication cycle of a Retrovirus. Available from: http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter18/animation_quiz_3.html)
Basic step in viral replication
| Step | Description |
| Attachment | attachment of the virus particle to the host cell receptor |
| Penetration | the virus is engulfed and enters host cell |
| Uncoating | viral genetic material is freed into host cytoplasm |
| Replication and synthesis | viral genetic material replicated, and viral proteins synthesized |
| Assembly | viral genetic material is packaged within capsid and proteins are packaged together |
| Release | virus will be released from the cell |