Q20 of 42 Page 1

Explain ‘mutation breeding’ as a method of developing disease resistant crop plants. Give an example of a pulse crop where this technique has helped.

Mutation breeding can be induced artificially through the use of chemicals or radiations, and also by selecting and using plants that have the desirable characters as a source in breeding. Example: In moong bean resistance to yellow mosaic virus/ powdery mildew were induced.


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10

State Gause’s ‘Competitive Exclusion Principle’. How have the recent studies modified this principle?

 19

Explain the phenomenon of evolution by natural selection as supported by the variations observed in white winged and dark winged moth populations in England between 1850 – 1920.

 21

Explain how ‘sticky ends’ are obtained in a DNA segment. Write their importance in DNA technology.

 27

(a) Work out the crosses so as to obtain the phenotypic ratios given below:

(i) 1 : 2 : 1 (in F2 generation)


(ii) 3 : 1 (in F2 generation)


(iii) 1 : 1 (in F1 generation)


(b) Differentiate between pleiotropy and polygenic inheritance patterns.


OR


(a) Describe the process of amino acylation.


(b) ‘‘Process of transcription and translation are coupled in prokaryotes, but not in eukaryotes.’’ Explain.