Amino acids: The building blocks of proteins.

CD4 T cells: Type of white blood cell. Play an important role in the immune system. Generally involved in activating other cells.

DNA: Genetic material of living organisms. Composed of four types of bases : Adenine (A), guanine (G), thymine (T) and cytosine (C). One base, a molecule of phosphate and a sugar form a nucleotide. DNA is double-stranded i.e. it consists of two polynucleotide chains. The sequence of bases in one chain determines that in the other - the two chains are said to be complimentary.

Enzyme: Catalysts of biological systems. Nearly all known enzymes are proteins. They are used to catalyse many chemical reactions and importantly are specific.

Integrase: Integrates HIV proviral DNA into the DNA of the host cell. Target for new drugs.

Nucleotide: a base molecule+a sugar+phosphate

Nucleoside: a base molecule+a sugar

Retrovirus: Contain a single strand of RNA. Replicate through DNA intermediates - Genetic information flows from RNA to DNA, DNA complimentary to viral RNA is synthesized in the host cell by reverse transcriptase, an enzyme brought into the cell by the infecting virus particle. Reverse transcriptase first catalyses the synthesis of DNA, then the digestion of RNA and finally the synthesis of a second strand of DNA.

Peptide: A chain of amino acids

Reverse transciptase: a viral enzyme. Catalyses synthesis of DNA from an RNA template. An enzyme which converts single-stranded RNA into double-stranded DNA. Making DNA from RNA is reverse transcription.

RNA: Genetic material, normally single stranded. Composed of four types of bases : Adenine (A), guanine (G), uracil (U) and cytosine (C).

Transcription: A section of DNA is copied to make RNA.

Virion: Complete extracellular form of a virus consisting of DNA or RNA surrounded by a coat.

Virus: Do not have a cellular structure and can only reproduce by invading living cells. They have a simple structure, consisting of a small piece of DNA or RNA, surrounded by a protective coat of protein (capsid). A few viruses have an additional layer around the capsid (envelope).