Acetyl group -- CH3CO.

Acetyl substituted Coenzyme A (Acetyl S-CoA) -- A key intermediate product in the metabolism of fats, proteins, and carbohydrates; it acts as a co-enzyme in subsequent biological acetylation processes of the citric acid cycle.

Adenylate -- A form of Adenosine monophosphate (AMP).

Amino acid -- The basic building block of proteins and polypeptides. It contains a basic amino group, an acidic carboxyl group, and a side chain attached to an alpha carbon atom. Amino acids link together by peptide bonds to form proteins, or function as chemical messengers and as intermediates in metabolism.

AMP, or Adenosine monophosphate -- One of the four nucleotides in a RNA molecule. Two phosphates are added to AMP to form ATP.

ATP, or Adenosine triphosphate -- Nucleoside triphosphate composed of adenine, ribose, and three phosphate groups that is the primary carrier of chemical energy in cells. The terminal phosphate groups are highly reactive in the sense that their hydrolysis, or transfer to another molecule, takes place with the release of a large amount of free energy.

Bacteriophage, or phage -- A virus that infects and lyses certain bacteria, such as E. Coli. Bacteriophages were discovered by Felix d'Herelle and Frederick Twort in the 1910s. In the 1940s, Max Delbruck encouraged the phage group at Cold Spring Harbor to concentrate their research on seven specific bacteriophages (T1 - T7), so that they could readily compare results. T2, T4, and T6 are serologically related and have large genomes. T3 and T7 are also related to each other serologically. T1 and T5 are not related to any other bacteriophages.

Carbohydrate -- Any of a group of organic compounds that includes sugars, starches, celluloses, and gums and serves as a major energy source in the diet of animals. These compounds are produced by photosynthetic plants and contain only carbon, hydrogen, and oxygen, with twice as many hydrogen atoms as oxygen atoms.

Cytokine -- Non-antibody immune system proteins released by one type of cell in response to a specific antigen.

Enzymatic adaptation, or enzymatic induction -- Increased synthesis of an enzyme by a cell or organism in response to a molecule, such as a hormone, produced by the cell or organism as the result of an exterior environmental signal.

Escherichia coli, or E. coli -- A common bacterium that has been studied intensively by geneticists because of its small genome size, normal lack of pathogenicity, and ease of culture in the laboratory.

Eukaryote -- An organism whose cells contain a nucleus. Eukaryotes include single, free-living cells such as yeasts, and multi-cellular organisms such as plants and animals.

Fatty acid -- A long chain of aliphatic carboxylic acid (organic, monobasic acids derived from hydrocarbons) found in natural fats and oils, it is also a component of membrane phospholipids and glycolipids.

Immunoglobulin -- Any of the structural related glycoproteins that function as antibodies in the immune system.

Interleukin -- Genetic term for a group of multifunctional cytokines that are produced by a variety of lymphoid and non-lymphoid cells of the immune system.

Messenger RNA, or mRNA -- An RNA molecule transcribed from the DNA of a gene, and from which a protein is translated by the action of ribosomes. The basic function of the nucleotide sequence of mRNA is to determine the amino acid sequence in proteins.

Methyl group -- An alkyl group (CH3) derived from methane by removal of one hydrogen atom.

Nucleoside -- A molecule composed of a purine or pyrimidine base covalently linked to a ribose or deoxyribose sugar. When nucleosides add a phosphate molecule, they become nucleotides, the building blocks of DNA and RNA.

Nucleotide -- A unit that polymerizes into nucleic acids (DNA or RNA). Each nucleotide consists of a purine (adenine or guanine) or pyrimidine (cytosine, thymine, or uracil) base, a sugar (ribose in the case of RNA, deoxyribose in the case of DNA), and a phosphate molecule.

Operators -- A DNA sequence adjacent to a prokaryotic gene that permits a repressor protein to control transcription of that gene (and often a group of consecutive genes as well).

Operons -- In prokaryotic chromosomes, a group of closely linked genes that produces a single messenger RNA in transcription and that consists of structural genes and regulating elements such as operators and promoters.

Phosphorylate -- To cause a chemical compound to take up or combine with phosphoric acid or a phosphorus-containing group.

Plasmid -- An extrachromosomal, circular, self-replicating DNA found in bacterial cells that carries genes for a variety of functions not essential for cell growth, e.g., antibiotic resistance, production of enzymes or toxins, or ability to metabolize certain nutrients.

Prokaryote -- A single-celled organism that lacks a nucleus.

Recombinant DNA, rDNA, hybrid strings -- Genetically engineered DNA prepared in vitro by cutting up DNA molecules and splicing together specific DNA fragments, usually from more than one type of organism, e.g., inserting pieces of virus DNA into a bacterial plasmid.

Repressor -- A protein that inhibits transcription of a gene by binding to a specific sequence of DNA nucleotides, e.g., to an operator.

Restriction enzyme -- An endonuclease which recognizes a specific sequence of bases in a DNA molecule. Each restriction enzyme has a single, specific recognition sequence, and binds to a DNA molecule at a specific site. As a result, treatment of a particular DNA molecule with a particular restriction enzyme will always produce the same set of DNA fragments.

Shotgun experiment -- In molecular biology, an experiment in which the whole DNA of an organism is cut up into small, gene-length segments using enzymes, and the individual segments then inserted into bacteria for cloning.

Simian virus 40 (SV 40) -- A polyomavirus isolated from Rhesus monkey kidney tissue, which transforms human and newborn kidney cell cultures into cancer cells, and on inoculation into newborn hamsters produces tumors. It does not produce cancer in humans or other primates.

Transfer RNA, or tRNA -- Small RNA molecules that carry amino acids to the ribosome for polymerization into a polypeptide. During translation, the amino acid is inserted into the growing polypeptide chain when the anticodon of the tRNA pairs with a codon on the mRNA (messenger RNA) being translated.