Glossary of Scientific Terms

Amino acid:
One of 20 different molecules that combine to form proteins. The sequence of amino acids in a protein determines the protein's structure and function.

Autosome:
Any chromosome not involved in determining an organism's sex. Humans have 22 pairs of autosomes in each cell.

Base:
One of the molecules - adenine, guanine, cytosine, thymine, or uracil - that form part of the structure of DNA and RNA molecules. The order of bases in a DNA molecule determines the structure of proteins encoded by that DNA.

Base pair:
Two complementary nucleotide bases joined together by chemical bonds. The two strands of the DNA molecule are held together in the shape of a double helix by the bonds between base pairs.

Base sequence:
The order of nucleotide bases in a DNA molecule.

Bioinformatics:
The science of informatics as applied to biological research. Informatics is the management and analysis of data using advanced computing techniques. It is particularly important as an adjunct to genomics research, because of the large amount of complex data this research generates.

Cell:
The basic subunit of any living organism, typically containing genetic material, an energy-producing system and other components, all surrounded by a wall and/or membrane.

Chromosome:
The DNA in a cell is divided into structures called chromosomes. They are large enough to be seen under a microscope. In humans, all cells other than germ cells usually contain 46 chromosomes: 22 pairs of autosomes and either a pair of X (in females) or an X chromosome and a Y chromosome (in males). In each pair of chromosomes, one is inherited from the father and one from the mother.

Clone:
A term applied to genes, cells or entire organisms that are derived from and are genetically identical to a single common ancestor gene, cell or organism, respectively. Cloning of genes and cells to create many copies in the laboratory is a common procedure essential for biomedical research.

DNA (deoxyribonucleic acid):
The genetic material of living organisms; the substance of heredity. It is a double-stranded, helical molecule that contains genetic instructions for growth, development and replication.

DNA microarray:
A wafer similar to a computer chip used to rapidly screen for the presence of particular genetic sequences.

DNA probe:
A piece of single-stranded DNA, typically labeled (with radioactivity or fluorescence) that can single out and bind with another specific piece of DNA. DNA probes can be used to determine the sequences present in a given length of DNA or the genes present in a sample of DNA.

Eukaryote:
A cell or organism with a membrane-bound, structurally discrete nucleus and other well-developed subcellular compartments. Eukaryotes include all organisms except viruses, bacteria and blue-green algae.

Gene:
A sequence of DNA that represents a fundamental unit of heredity. Most genes encode proteins, but some code for RNA molecules.

Gene expression:
The process by which the information encoded in a gene is converted into protein or some form of RNA. The DNA sequence is first transcribed into RNA and then usually translated into protein.

Gene therapy:
Treatment of a disease by introducing a new gene into a cell. The new gene may be used to replace a function that is missing because of a defective gene, to help protect normal cells from the effects of drugs (such as those used to treat cancer) or to protect cells from viruses.

Genotype:
The genetic makeup ­ DNA sequence ­ of an individual at one or more places in the genome.

Genetic disease:
A disease caused by a genetic mutation that is either inherited or arises spontaneously.

Genome:
The total genetic information of a particular organism. The normal human genome consists of 3 billion base pairs of DNA.

Genomics:
The study of the structure and function of large numbers of genes simultaneously. Advances in genomics will revolutionize our understanding of the molecular mechanisms of disease, including the complex interplay of genetic and environmental factors. Genomics is also stimulating the discovery of breakthrough health-care products by revealing thousands of new biological targets for the development of drugs and by giving scientists innovative ways to design new drugs, vaccines and DNA diagnostics.

Nucleic acid:
One of the family of molecules that includes the DNA and RNA molecules. Nucleic acids were so named because they were originally discovered within the nucleus of cells, but they have since been found to exist outside the nucleus as well.

Nucleotide:
The "building block" of nucleic acids, such as the DNA molecule. A nucleotide consists of one of four bases ­ adenine, guanine, cytosine, or thymine ­ attached to a phosphate-sugar group. In DNA the sugar group is deoxyribose, while in RNA (a DNA-related molecule which helps to translate genetic information into proteins), the sugar group is ribose, and the base uracil substitutes for thymine.

Nucleus:
The membrane-bound structure containing a cell's central DNA found within all eukaryotic cells.

Pharmacogenomics:
The science of understanding the relationship between genetic makeup (genotype) and response to drug treatment. Some drugs work well in some patient populations and not as well in others. Studying the genetic basis of response to therapeutics allows drug developers to more effectively design therapeutic treatments.

Peptide:
Two or more amino acids chained together by a bond called a "peptide bond." A protein is a long chain of amino acids joined together in this way, and, therefore, is sometimes referred to as a "polypeptide." Some proteins contain more than one polypeptide chain.

Polymerase chain reaction (PCR):
A method for creating millions of copies of a particular segment of DNA. If a scientist needs to detect the presence of a very small amount of a particular DNA sequence, PCR can be used to amplify the amount of that sequence until there are enough copies available to be detected.

Protein:
A molecule composed of amino acids linked together in a particular order specified by a gene's DNA sequence. As the chain of amino acids is being synthesized, it is also folded into higher order structures shaped, for example, like helices or flat sheets. Proteins are required for the structure, function and regulation of cells, tissues and organs in the body.

Proteomics:
The study of the proteins that genes produce and the changes in protein expression patterns in different environments and conditions.

RNA (ribonucleic acid):
A molecule similar to DNA, which helps in the process of decoding the genetic information carried by DNA.

Sequencing:
The process of determining the order of nucleotides in a DNA or RNA molecule, or determining the order of amino acids in a protein.

Vector:
A delivery system, such as a modified virus, for carrying and inserting a gene into a target cell.