Questions: describe the physical and genomic features of viruses, understand how viruses are classified and grouped, describe the 5-step infection cycle for enveloped and non-enveloped viruses, list the difference between acute and persistent infections. Infection with a virus typically causes damage to the host cell: virus was first discovered in tobacco leaves, a complete virus entity is called a virion. Viral envelopes: viral envelopes are part host, and part virus, envelope carbohydrates and lipids come from the host, envelope proteins (spikes) are virally-encoded. Viral genomes: the striking difference between viruses and other cellular organisms is the nature of their genome, cellular dna is always double standard (dsdna), but viruses can have single stranded dna (ssdna). However, dsdna is still more common: also dna can be really segmented and each segment usually codes for one protein. Animal virus replication: occurs in 5 steps, attachment: viral spikes bind receptors on plasma membrane. Some viruses cause cells to lyse during release.