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

$(a)$ Reduce usage of chemical pesticides : $Bt$ toxin is produced by a bacterium called Bacillus thuringiensis ($Bt$ for short). $Bt$ toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides; It acts as a bio-pesticide. Examples are $Bt$ cotton, $Bt$ corn, rice, tomato, potato and soybean etc.

$(b)$ Enhance nutritional value of food crops : Golden rice is the transgenic variety of basmati rice which gives high yield and rich in vitamin $A$, so it is used in the deficiency of vitamin-$A$ causing night blindness and skin disorder.