The genetic composition of all living creatures is continually undergoing alteration by mutation, natural selection, and genetic drift. Beginning at the onset of plant and animal to enhance their health and usefulness to humans by selecting for specific phenotypic traits development of recombinant DNA technology has enabled scientists to isolate single genes analyze and modify their nucleotide structures make copies of these isolated genes and insert copies of these genes into genome of plants or animals the procedure used to insert these isolated genes is called gene transfer an animal that contains the inserted gene or genes is called a transgenic animal and the transferred gene is called a transgenedomestication, humans have further manipulated the genetic composition of plant and animals to enhance their health and usefulness to humans by selecting for specific phenotypic traits