How is viral genetic material inserted into animal cells?
Depends on the identities of the Virus and the Host..
There are three main mechanisms for infection:
- Genetic injection,
- Membrane Fusion
Genetic injection occurs primary in the case of bacteria, so we'll leave that out as you asked about animal cells....
In Viruses, the genetic material (DNA or RNA) is enclosed in a protein shell called a Capsid . This capsid contains proteins called Receptors. When a virus particle (" Virion ") bumps into a suitable host cell, these receptors bind to susceptible receptors on the membrane of the host cell. After that, either of two things can happen:
Some viruses have, after their formation and upon lysis of the (dying) host cell, picked up pieces of the membrane of the host cell.
This forms an Envelope around the capsid, and mainly consists of a phospholipid bilayer and membrane proteins. It also often contains viral Glycoproteins, which serve as the receptors needed for binding to the new host cell.
If there is an Envelope, after attachment this envelope will fuse with the Host Cell membrane , and the complete virus will enter the cell.
If the viral capsid doesn't have an envelope, its attachment to the membrane will initiate the forming of a vesicle that will transport it into the cell. It basically tricks the cell into "thinking" that food has arrived...
Once the vesicle is opened within the cell, the capsid will be broken open by Proteases (lytic enzymes) that will free the DNA/RNA content.
Footnote: Plant cells have a much thicker cell wall, and consewquently a virus has some extra hurdles to overcome, but this question was about Animal cells..