Follow Us


12th Biology 2013 Set2 Delhi Board Paper Solution

Question 28

Describe the asexual and sexual phases of life cycle of Plasmodium that causes malaria in humans.
OR
(a) What is plant breeding? List the two steps the classical plant breeding involves.
(b) How has the mutation breeding helpes in improving crop varieties? Give one example where this technique has helped.
(c) How has the breeding programme helped in improving the public nutritional health? State two examples in support of your answer.

Answer

OR

Ans. (a) Plant breeding: It is manipulation of plant species so as to produce plants with desired characters like better yield and disease resistance.
 
Classical plant breeding involves
 
(i) Hybridisation of pure lines.
 
(ii) Artificial selection for producing plant with desired characters of higher yield or resistance to diseases.
 
(b) Mutational breeding- creates genetic variations through changes in the base sequences within genes.
This results in new character which is not found in parents. Improved varieties can be produced by  inducing mutations artificially in the plants having desirable characters.
 
For example in mung bean resistance to yellow mosaic virus and powdery mildew was induced by limitations.
 
(c) Breeding crops with higher levels of vitamins and minerals or higher proteins and healthier fats has improved public health.
 
Breeding programmes have been designed with objectives of
 
(i) improved protein content and quality.
(ii) Oil content and quality
(iii) Vitamin content
(iv) Micronutrients and mineral contains
maize hybrids having double amount of lysine and tryopophan have been developed. Similarly IARI New Delhi have developed many vegetable crops rich in vitamins and minerals like spinach, carrots, pumpkin etc.