An ambitious EC-funded research initiative on epigenetics advancing towards systems biology

Most widely used definition: A gene is a basic unit of DNA. It is transcribed into RNA molecules which either serve as a template to generate a polypeptide chain or fullfill regulatory, structural or catalytic functions. 2. More basic definition used by Richard Dawkins: A gene is defined as any portion of chromosomal material that potentially lasts for enough generations to serve as a unit of natural selection.

Genes that are expressed are made into RNA (transcribed by RNA polymerase). The RNA transcript may subsequently be converted to protein (translated). Not all genes (e.g. rRNA, tRNA genes) are translated into protein.

A fixed position on a chromosome that is occupied by a given gene or one of its alleles.

Descriptive representation of the structure of a gene. It includes the DNA sequence of a gene with introns and exons, 3' or 5' transcribed-untranslated regions, termination/poly-adenylation signal, regulatory elements such as promoters, enhancers and it may include known mutations defining alternative alleles of the same gene.

The modulation of gene expression. Genes are regulated at the level of DNA, RNA and protein, the interactions between which are a direct consequence of their immediate biochemical environment.

The insertion of genes into an individual's cells and tissues to treat a disease, and hereditary diseases in particular. Gene therapy typically aims to supplement a defective mutant allele with a functional one. Although the technology is still in its infancy, it has been used with some success.

An RNA molecule of defined size over the length of a gene.

A cell uses a gene as a template to make a transcript (or mRNA molecule); this transcript will be further processed and then be translated to make a protein.

Three bases (e.g. 5'CGC3') in a DNA or RNA sequence specify a codon, which codes for an amino acid (e.g. arginine) in a protein. Genes are frequently tens of thousands of base-pairs long. Usually the codons of an exon are in phase within an uninterrupted open reading frame giving rise to long chains of amino acids after ribosomal translation.

A disease caused by genetic mutation and/or epimutaion(s).

Modification of the natural DNA sequence of a gene or genes. Genetic engineering is the basis of the modern biotechnological revolution, to which we owe such inventions as insulin-producing bacteria.

That contained within the DNA or RNA sequence.

Basis of genetic engineering, which alters the natural DNA sequence of an organism, either by adding foreign DNA which may or may not be inherited stably within the cells or by inducing specific genetic mutations serving experimental or medical purpose in any arbitrary sequence in vivo (gene targeting).

A natural change in the DNA at a particular locus in an organism. The term is used loosely to include point mutations (concerning a single nucleotide) as well as chromosomal changes such as translocations, deletions and inversion of larger DNA segments. Also transposable elements are responsible for mutations in various ways.

A complete set (n) of chromosomes (hence, of genes) inherited as a unit from one parent plus one sex chromosome from the other parent in heterogametic individuals. The full genome sequences are available for hundreds of bacteria and viruses, human, and model organisms like mouse, frog, worm and fruit flies.