HIV viruses emerging from a T-cell
A retrovirus is a virus that infects the cells of host organisms in order to reproduce in a particular way.

They reproduce by hijacking the host cell's normal mechanisms of transcription and translation, mechanisms that 'read' DNA to make RNA and proteins.

The hijack is accomplished by what is called reverse transcription.

Reverse transcription involves translating the virus' RNA genome into DNA, then inserting this DNA into the host cell's own DNA.

When the DNA is 'read' by the cell, the RNA and proteins produced create more copies of the original virus.

It is important to be familiar with retroviruses in a bit more detail in order to appreciate how endogenous retroviruses provide such convincing evidence for common descent between different kinds of creatures. Click here to continue.