The plants obtained through genetic engineering contain a gene or genes usually from an unrelated organism, such genes are called transgenes and the plants containing transenes are known as transgenic plants. These plants are often called as genetically modified or $GM$ crops, e.g., Flavr savr tomatoes, golden rice. Plants are made transgenic for identification, expressing the gene activity in time, to produce several chemicals like fatty acids, sugars, cellulose, rubber, etc