Biotechnology is the use of plants, animals and micro-organisms to create new products or processes. It includes using bacteria or enzymes to make industrial processes work more efficiently and create less pollution, or to clean up thé environment. One kind of biotechnology is gene technology, sometimes called 'genetic engineering' or 'genetic modification', where the genetic material of living things is deliberately altered to enhance or remove a particular trait and allow the organism to perform new functions. Genes within a species can be modified, or genes can be moved from one species to another. Gene technology is the term given to a range of activities concerned with understanding the expression of genes, taking advantage of natural genetic variation, modifying genes and transferring genes to new hosts. This book on gene biotechnology is being prepared by keeping in view the requirement of the students and researchers in biotechnology, genetic engineering and other allied fields.