HGNC. Symbols are chosen to be unique, and each gene has only one symbol (although approved symbols sometimes change). Symbols are preferably kept consistent with other members of a gene family and with homologs in other species, particularly the mouse due to its role as a common model organism. Genetic engineering Genetic engineering is the modification of an organism's genome through biotechnology. Since the 1970s, a variety of techniques have been developed to specifically add, remove and edit genes in an organism. Recently developed genome engineering techniques use engineered nuclease enzymes to create targeted DNA repair in a chromosome to either disrupt or edit a gene when the break is repaired. The related term synthetic biology is sometimes used to refer to extensive genetic engineering of an organism. Genetic engineering is now a routine research tool with model organisms. For example, genes are easily added to bacteria and lineages of knockout mice with a specific gene's function disrupted are used to investigate that gene's function. Many organisms have been genetically modified for applications in agriculture, industrial biotechnology, and medicine. For multicellular organisms, typically the embryo is engineered which grows into the adult genetically modified organism. However, the genomes of cells in an adult organism can be edited using gene therapy techniques to treat genetic diseases. See also References Citations Sources Main textbook – A molecular biology textbook available free online through NCBI Bookshelf. Glossary Ch 1: Cells and genomes 1.1: The Universal Features of Cells on Earth Ch 2: Cell Chemistry and Biosynthesis 2.1: The Chemical Components of a Cell Ch 3: Proteins Ch 4: DNA and Chromosomes 4.1: The Structure and Function of DNA 4.2: Chromosomal DNA and Its Packaging in the Chromatin Fiber Ch 5: DNA Replication, Repair, and Recombination 5.2: DNA Replication Mechanisms 5.4: DNA Repair 5.5: General Recombination Ch 6: How Cells Read the Genome: From DNA to Protein 6.1: DNA to RNA 6.2: RNA to Protein Ch 7: Control of Gene Expression 7.1: An Overview of Gene Control 7.2: DNA-Binding Motifs in Gene Regulatory Proteins 7.3: How Genetic Switches Work 7.5: Posttranscriptional Controls 7.6: How Genomes Evolve Ch 14: Energy Conversion: Mitochondria and Chloroplasts 14.4: The Genetic Systems of Mitochondria and Plastids Ch 18: The Mechanics of Cell Division 18.1: An Overview of M Phase 18.2: Mitosis Ch 20: Germ Cells and Fertilization 20.2: Meiosis Further reading External links Comparative Toxicogenomics Database DNA From The