Genetic engineering, also called genetic modification, is the direct manipulation of an organism's genome using biotechnology. New DNA may be inserted in the host genome by first isolating and copying the genetic material of interest using molecular cloning methods to generate a DNA sequence, or by synthesizing the DNA, and then inserting this construct into the host organism. Genes may be removed, or "knocked out", using a nuclease. Gene targeting is a different technique that uses homologous recombination to change an endogenous gene, and can be used to delete a gene, remove exons, add a gene, or introduce point mutations. An organism that is generated through genetic engineering is considered to be: Genetic engineering of plants is much easier than that of animals. There are several reasons for this: (1) there is a natural transformation system for plants (the bacterium Agrobacterium tumefaciens), (2) plant tissue can redifferentiate (a transformed piece of leaf may be regenerated to a whole plant), and (3) plant transformation and regeneration are relatively easy for a variety of plants.Genetic engineering techniques have been applied in numerous fields including research, agriculture, industrial biotechnology, and medicine. Genetic engineering alters the genetic make-up of an organism using techniques that remove heritable material or that introduces DNA prepared outside the organism either directly into the host or into a cell that is then fused or hybridized with the host. This involves using recombinant nucleic acid (DNA or RNA) techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro-injection, macro-injection and micro-encapsulation techniques.