Why do viruses need to use host cell proteins?
Viruses travel light. Their genomes are very small, and often encode very few proteins. This means that they don’t have space for enough genes to encode all the proteins they need to replicate their DNA. However, they can afford to be so economical with their genes because they simply help themselves to the proteins they need from their host cell. This is why viruses are sometimes described as cellular parasites. What is a retrovirus? A retrovirus is a special kind of RNA virus that infects eukaryotic cells. It is called a retrovirus because it copies its RNA genome into DNA when it enters a host cell, in contrast to the usual situation when instructions in DNA are copied to make RNA. The virus that causes AIDS (HIV) is a retrovirus. How does a retrovirus infect a cell and replicate its genome? Retroviruses enter the host cell, then uncoat their RNA genome (get rid of their protein coats). Together with their RNA, these viruses carry a small amount of an enzyme called reverse transcrip
