Human immunodeficiency virus (HIV) is a retrovirus. The shape of the virus is spherical. The virus is composed of a capsid (protein) coat which contains the genetic material, RNA. The genome of HIV contains two helices of RNA molecules in folded form. The protein envelope has many spikes of glycoprotein. The outer part of glycoprotein is gp120, which is attached to the inner part of the glycoprotein, gp41. The enzyme reverse transcriptase is responsible for the conversion of the viral RNA to form the DNA. There is another enzyme called as integrase which helps the viral genome to get incorporated into the host cell.