<P> Recombinant DNA is widely used in biotechnology, medicine and research . Today, recombinant proteins and other products that result from the use of DNA technology are found in essentially every western pharmacy, doctor's or veterinarian's office, medical testing laboratory, and biological research laboratory . In addition, organisms that have been manipulated using recombinant DNA technology, as well as products derived from those organisms, have found their way into many farms, supermarkets, home medicine cabinets, and even pet shops, such as those that sell GloFish and other genetically modified animals . </P> <P> The most common application of recombinant DNA is in basic research, in which the technology is important to most current work in the biological and biomedical sciences . Recombinant DNA is used to identify, map and sequence genes, and to determine their function . rDNA probes are employed in analyzing gene expression within individual cells, and throughout the tissues of whole organisms . Recombinant proteins are widely used as reagents in laboratory experiments and to generate antibody probes for examining protein synthesis within cells and organisms . </P> <P> Many additional practical applications of recombinant DNA are found in industry, food production, human and veterinary medicine, agriculture, and bioengineering . Some specific examples are identified below . </P> <Dl> <Dt> Recombinant chymosin </Dt> <Dd> Found in rennet, chymosin is an enzyme required to manufacture cheese . It was the first genetically engineered food additive used commercially . Traditionally, processors obtained chymosin from rennet, a preparation derived from the fourth stomach of milk - fed calves . Scientists engineered a non-pathogenic strain (K - 12) of E. coli bacteria for large - scale laboratory production of the enzyme . This microbiologically produced recombinant enzyme, identical structurally to the calf derived enzyme, costs less and is produced in abundant quantities . Today about 60% of U.S. hard cheese is made with genetically engineered chymosin . In 1990, FDA granted chymosin "generally recognized as safe" (GRAS) status based on data showing that the enzyme was safe . </Dd> <Dt> Recombinant human insulin </Dt> <Dd> Almost completely replaced insulin obtained from animal sources (e.g. pigs and cattle) for the treatment of insulin - dependent diabetes . A variety of different recombinant insulin preparations are in widespread use . Recombinant insulin is synthesized by inserting the human insulin gene into E. coli, or yeast (Saccharomyces cerevisiae) which then produces insulin for human use . </Dd> <Dt> Recombinant human growth hormone (HGH, somatotropin) </Dt> <Dd> Administered to patients whose pituitary glands generate insufficient quantities to support normal growth and development . Before recombinant HGH became available, HGH for therapeutic use was obtained from pituitary glands of cadavers . This unsafe practice led to some patients developing Creutzfeldt--Jakob disease . Recombinant HGH eliminated this problem, and is now used therapeutically . It has also been misused as a performance - enhancing drug by athletes and others . DrugBank entry </Dd> <Dt> Recombinant blood clotting factor VIII </Dt> <Dd> A blood - clotting protein that is administered to patients with forms of the bleeding disorder hemophilia, who are unable to produce factor VIII in quantities sufficient to support normal blood coagulation . Before the development of recombinant factor VIII, the protein was obtained by processing large quantities of human blood from multiple donors, which carried a very high risk of transmission of blood borne infectious diseases, for example HIV and hepatitis B. DrugBank entry </Dd> <Dt> Recombinant hepatitis B vaccine </Dt> <Dd> Hepatitis B infection is controlled through the use of a recombinant hepatitis B vaccine, which contains a form of the hepatitis B virus surface antigen that is produced in yeast cells . The development of the recombinant subunit vaccine was an important and necessary development because hepatitis B virus, unlike other common viruses such as polio virus, cannot be grown in vitro . Vaccine information from Hepatitis B Foundation </Dd> <Dt> Diagnosis of infection with HIV </Dt> <Dd> Each of the three widely used methods for diagnosing HIV infection has been developed using recombinant DNA . The antibody test (ELISA or western blot) uses a recombinant HIV protein to test for the presence of antibodies that the body has produced in response to an HIV infection . The DNA test looks for the presence of HIV genetic material using reverse transcription polymerase chain reaction (RT - PCR). Development of the RT - PCR test was made possible by the molecular cloning and sequence analysis of HIV genomes . HIV testing page from US Centers for Disease Control (CDC) </Dd> <Dt> Golden rice </Dt> <Dd> A recombinant variety of rice that has been engineered to express the enzymes responsible for β - carotene biosynthesis . This variety of rice holds substantial promise for reducing the incidence of vitamin A deficiency in the world's population . Golden rice is not currently in use, pending the resolution of regulatory and intellectual property issues . </Dd> <Dt> Herbicide - resistant crops </Dt> <Dd> Commercial varieties of important agricultural crops (including soy, maize / corn, sorghum, canola, alfalfa and cotton) have been developed that incorporate a recombinant gene that results in resistance to the herbicide glyphosate (trade name Roundup), and simplifies weed control by glyphosate application . These crops are in common commercial use in several countries . </Dd> <Dt> Insect - resistant crops </Dt> <Dd> Bacillus thuringeiensis is a bacterium that naturally produces a protein (Bt toxin) with insecticidal properties . The bacterium has been applied to crops as an insect - control strategy for many years, and this practice has been widely adopted in agriculture and gardening . Recently, plants have been developed that express a recombinant form of the bacterial protein, which may effectively control some insect predators . Environmental issues associated with the use of these transgenic crops have not been fully resolved . </Dd> </Dl>

Give two examples of how recombinant dna has been used in food production