A virus is made up of a DNA or RNA genome inside a protein shell called a capsid. Some viruses have an external membrane envelope. Viruses are very diverse. They come in different shapes and …

Viral replication has two cycles: lytic and lysogenic. In the lytic cycle, viruses quickly take over the host cell, make many copies, break the cell, and infect other cells.

In simple terms, a retrovirus is a type of virus that uses RNA as its genetic material instead of DNA. When it infects a cell, it uses an enzyme called reverse transcriptase to convert its RNA into DNA, …

The integrated phage DNA, called a prophage, is not active: its genes aren't expressed, and it doesn't drive production of new phages. However, each time a host cell divides, the prophage is copied …

In the lysogenic cycle, a virus infects a host cell and then integrates its genetic material into the host's DNA. The viral genetic material is replicated along with the host's DNA whenever the cell divides.

How Alfred Hershey and Martha Chase showed conclusively that DNA is the genetic material.

A mutation is a permanent change in the genetic material (DNA or RNA) of a virus. A mutation can happen if there is a mistake during copying of the DNA or RNA of the virus.

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A typical viral infection cycle includes attachment to a host cell, entry of the virus’s genetic material, viral replication, self-assembly, and release. Created by Sal Khan.

A virus’s genetic material can be made up of either DNA or RNA. These nucleic acids contain genes that provide the host cell with instructions for making new viruses.