GAMMA INTERFERON: A T cell-derived stimulating substance that suppresses virus reproduction, stimulates other T cells and activates macrophage cells. See also Macrophage; T Cells.

GANGLION: A mass of nervous tissue, composed principally of nerve-cell bodies, usually lying outside the central nervous system.

GASTROINTESTINAL: Relating to the stomach and intestines.

GENE: 1. A unit of DNA that carries information for the biosynthesis of a specific product (in the cell). 2. Ultimate unit by which inheritable characteristics are transmitted to succeeding generations in all living organisms. Genes are contained by, and arranged along the length of, the chromosome. The gene is composed of deoxyribonucleic acid (DNA). Each chromosome of each species has a definite number and arrangement of genes, which govern both the structure and metabolic functions of the cells and thus of the entire organism. They provide information for the synthesis of enzymes and other proteins and specify when these substances are to be made. Alteration of either gene number or arrangement can result in mutation (a change in the inheritable traits). See also DNA.

GENETIC ENGINEERING: Group of new research techniques that manipulate the DNA (genetic material) of cells. The gene-splicing technique, which produces recombinant DNA, is a method of transporting selected genes from one species to another. For example, in this technique, the genes, which are actually portions of molecules of DNA, are removed from the donor (insect, plant, mammal or other organism) and spliced into the genetic material of a virus; then the virus is allowed to infect recipient bacteria. In this way the bacteria become recipients of both viral and foreign genetic material. When the virus replicates within the bacteria, large quantities of the foreign as well as viral material are made.

GENOME: The complete set of genes in the chromosomes of each cell of a particular organism. See also Gene.

GP41: Glycoprotein 41, a protein embedded in the outer envelope of HIV. Plays a key role in HIV's infection of CD4+ T cells by facilitating the fusion of the viral and the cell membranes. See also CD4 (T4) or CD4+ Cells; Envelope.

GP120: Glycoprotein 120, a protein that protrudes from the surface of HIV and binds to CD4+ T cells. See also CD4 (T4) or CD4+ Cells.

GP160: Glycoprotein 160, a precursor of HIV envelope proteins gp41 and gp120.