Genetic Terms Adeno-associated viruses (AAVs) A group of viruses able to get inside many different types of cells throughout the body. Cell Sometimes called the “building blocks of life,” cells are structural, functional, and biological units of life. They contain the nucleus at their center, which holds a cell’s genetic materials. This is where genes are delivered for gene replacement therapy. Deoxyribonucleic acid (DNA) The carrier of the body’s genetic information, DNA contains the information used by the body to make every substance in our body, such as proteins. It is made up of two strands of molecules that wind around each other in a double helix, a structure like a twisted ladder. Gene replacement Gene replacement uses a new, working gene to replace the function of a nonworking or missing gene. This gene then provides the instructions for the body to make the missing or insufficient protein. Learn more about gene replacement Gene The basic units of heredity, genes, which are small sections of DNA, carry the instructions cells need to make proteins used throughout the body. Gene addition The addition of new therapeutic genes that target a specific cause of disease. Gene editing Also called genome editing, this treatment inserts, removes, or changes specific pieces of a person’s existing DNA to correct a gene mutation. Learn more about gene editing Gene inhibition This treatment deactivates or “silences” the expression of a mutant gene that codes for a toxic protein or too much protein. Learn more about gene inhibition Gene therapy Gene therapy is a treatment strategy for disorders caused by a missing or faulty gene and may involve addition, inhibition, editing, or functional replacement of a gene. Genetic disease This type of disease is caused by a missing or nonworking gene or genes. It may be inherited from one or both parents or can happen due to random errors. Monogenic diseases are those caused by mutations in a single gene. Learn more about genetic diseases Nucleus This is the control center of a cell and is where all of the cell’s genetic material, or DNA, is stored. This is also where the vector carries the new, working gene when undergoing gene replacement therapy. Vector A vehicle used to carry a working copy of a gene into the nucleus of a cell. It is usually made of a virus that has been changed so that it can no longer make a person sick.