Vaccines are preventive medicines which when introduced into the body protect it from a specific disease-causing agent. These are usually derived from the disease-causing agent itself which may be a microbe like bacteria or virus, or a toxic microbial product called toxoid.
Vaccines stimulate the immune system of the body to produce neutralizing substances called antibodies as soon as the disease-causing agent enters the body. Vaccines that protect against a microbial disease usually contain the live but weakened or the dead microbe itself. Vaccines for some viral diseases are also prepared from parts of the disease-causing viruses. For diseases such as tetanus or cholera which are caused by toxoids, vaccines are made from chemically inactivated toxoids. Vaccines also contain preservative chemicals and substances called adjuvants which make the immune system react faster and more strongly. Familiar vaccines such as DPT given to children are special preparations for protecting against several diseases simultaneously. DPT protects against diphtheria, pertussis (whooping cough) and tetanus.
The word plastics come from the Greek word Plastikos which means ‘to shape’ or ‘able to be moulded’. All plastics are man-made polymers containing repeat units of the same group called monomer. The process by which plastics are made is called polymerization. The starting materials from which plastics are made are obtained from natural gas and crude oil.
Plastic money refers to the use of instruments like credit cards instead of cash in business transactions. It is called plastic money because credit cards are made of plastic. At present currency notes, cheques made of paper or coins are used to make payments after a purchase. Credit cards can also be used to withdraw cash from automatic teller machines. Some credit cards are used exclusively for paying call charges in public telephone booths. Plastic money also carries information about its holder in coded form which makes it theft-proof. No one, but the holder is able to use the card.
Genetic engineering is a technique of manipulating the DNA in cells to endow an organism with qualities it did not naturally possess. The technique is also called gene manipulation. It entails a number of steps the first of which is the constitution of DNA segment from nucleic acid molecules in a test tube. The length of DNA so made is inserted into a virus or some other suitable vector that can serve as a molecular ferry to carry it into the host organism. The crucial factor here is ability of the inserted DNA molecule to express itself and also to multiply. Bacteria and even higher animals may be genetically engineered to produce foreign proteins of interest by inserting a copy or multiple copies of the gene coding for the protein into them. Several important products of medical use such as insulin and the human growth hormone are now being produced commercially using genetically engineered bacteria. ‘Tracy’, a genetically engineered sheep produces the pharmaceutically important protein called Alpha-1 antitrypsin in her milk. Genetic engineering may be used to boost growth, alter resistance to factors such as drugs, heat, cold and salinity in both animals and plants. 
Gene therapy is a new and as yet largely experimental branch of medicine that incorporates techniques of genetic engineering to correct inherited disorders or in-born errors of metabolism. The idea of curing a genetic disorder by repairing or replacing a faulty gene or gene product (protein) first occurred to Dr. W. French Anderson now recognized as the father of gene therapy.
its normal version are produced in the laboratory by cloning. Then suitable host cells are selected from the patient’s body and genetic engineering is used to transfer copies of the normal version of the gene into it. The doctored cells are then returned to the body by injection. The introduced genes are incorporated into the chromosomes of the patient’s cells and propagate with each cell division. Since the introduced genes work normally and produce the protein that was previously either absent or malformed, the error is corrected in the victim who gets cured of the symptom. However, since gene therapy is not approved for genetic manipulation of the germ or reproductive cells, the cure cannot be passed onto future generations of the cured victims.