vector /vek″tər/ [L, carrier] , 1. a quantity having direction and magnitude, usually depicted by a straight arrow. The length of the arrow represents magnitude, and the head represents direction. 2. a carrier, especially one that transmits disease. A biological vector is usually an arthropod in which the infecting organism completes part of its life cycle. A mechanical vector transmits the infecting organism from one host to another but is not essential to the life cycle of the parasite. Kinds of vectors include dogs, which carry rabies; mosquitoes, which transmit malaria; and ticks, which carry Rocky Mountain spotted fever. 3. a retrovirus that has been modified by alteration of its genetic component. Through recombinant deoxyribonucleic acid techniques, genes that cause harmful effects such as cancer are removed and genes that mediate synthesis of essential enzymes are added. The vector then can be injected into a patient who suffers from an enzyme deficiency, such as Lesch-Nyhan syndrome. −vectorial, adj., −vector, v.
