Explain brifly what is Genetic Engineering ?

Genetic Engineering : Engineering techniques have been used in agriculture and horticulture for centuries. Certain plants or animals were chosen over others to be grown for prized traits, leading to continuation of the species. Examples are hunting dogs, cattle, and various species of grain.

Breeding with the goal of maintaining or enhancing prized traits is called inbreeding, and the resulting generations are called purebred. However, excessive inbreeding increases the likelihood that harmful recessive genes will be homozygous. For this reason, breeders often crossbreed related varieties of plants or animals. The phenomenon by which hybrids often grow larger and healthier than either parent is called hybrid vigor.

Biologists sometimes induce mutations in various organisms and choose mutants with desired traits from their progeny. X-rays are often used for this purpose, since they leave no toxic residue. Geneticists improve the size of fruits and flowers by induced polyploidy through the use of colchicine, a drug that breaks down cytoplasmic microtubules and prevents formation of cell walls. Mitosis occurs without cell division, so the cells become polyploid. Berries from artificially polyploid plants are much larger than normal berries although close to half of flowering plant species are naturally polyploid. While polyploid organisms must be normally be mated with others of the same ploidy, many plants avoid this problem by self-fertilizing, producing offspring of the same ploidy.

The term genetic engineering now generally refers to the manipulation of genes by sophisticated techniques of recombinant DNA technology.