Explain with the help of one example how genetically modified plants can:
$(a)$ Reduce usage of chemical pesticides.
$(b)$ Enhance nutritional value of food crops.

(N/A) Reduce usage of chemical pesticides: $Bt$ toxin is produced by a bacterium called $Bacillus$ $thuringiensis$ ($Bt$ for short). The $Bt$ toxin gene has been cloned from the bacteria and expressed in plants to provide resistance to insects without the need for synthetic insecticides. It acts as a bio-pesticide. Examples include $Bt$ cotton,$Bt$ corn,rice,tomato,potato,and soybean.
$(b)$ Enhance nutritional value of food crops: Golden rice is a transgenic variety of rice that is engineered to be rich in Vitamin $A$ (beta-carotene). It is used to combat Vitamin $A$ deficiency,which causes night blindness and other health disorders.