Genes are carried on chromosomes, are the basic physical and functional units of heredity. Genes are specific sequences of bases that encode instructions on how to make proteins. Although genes get a lot of attention, it?s the proteins that perform most life functions and even make up the majority of cellular structures. When genes are altered so that the encoded proteins are unable to carry out their normal functions, genetic disorders can result. Gene therapy is a technique for correcting defective genes responsible for disease development. Researchers may use one of several approaches for correcting faulty genes: ? A normal gene may be inserted into a nonspecific location within the genome to replace a nonfunctional gene. This approach is most common. ? An abnormal gene could be swapped for a normal gene through homologous recombination. ? The abnormal gene could be repaired through selective reverse mutation, which returns the gene to its normal function. ? The regulation (the degree to which a gene is turned on or off) of a particular gene could be altered.