What is the essential difference between retroviruses and other viruses

Retroviruses contain an enzyme called reverse transcriptase. This enzyme allows the virus to "convert" it's RNA into DNA so it can be inserted into the hosts own DNA. This is how the HIV virus works.

Definitions of RETROVIRUS on the Web:

a class of enveloped viruses that have their genetic material in the form of RNA and use the reverse transcriptase enzyme to translate their RNA into DNA in the host cell.

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A type of virus that has RNA instead of DNA as its genetic material. It uses an enzyme called reverse transcriptase to become part of the host cells' DNA. This allows many copies of the virus to be made in the host cells. The virus that causes AIDS, the human immunodeficiency virus (HIV), is a type of retrovirus.

www.stjude.org/glossary

A family of RNA viruses that have the unique characteristic of producing an enzyme that makes a DNA copy of its genetic information from an RNA template (the opposite of what normally takes place). The most widely recognized of these viruses is HIV, the causative agent in AIDS. Another virus from this family (HTLV-1) has been associated with T cell leukemia. Initial reports of an association of an HTLV-II-like retrovirus with CFS could not be confirmed in subsequent studies.

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