NEET Botany Molecular Basis of Inheritance Questions Solved

BOARD

(a) A DNA segment has a total 1,000 nucleotides, out of which 240 of them are adenine

containing nucleotides. How many pyrimidine bases this DNA segment possesses?     1

(b) Draw a diagrammatic sketch of a portion of DNA segment to support your answer.2

(a) 1. Purines        =  Adenine, Guanine

      Pyrimidines   = Cytosines and Thymine

     2. Purines A always pair with T

        and C always pair with G

     So if 240 adenine are there in the segment, then 240 thymine will pair with them.

                Purines                      Pyrimidines

                  240                            240             = 480

               Adenine                       Thymine  

    Now, 1000- 480 = 520 then,

               Cytosine                       Guanine

                 260                               260          

    Total number of pyrimidines are = 240 + 260 = 500
      

 (b) Diagrammatic sketch of a DNA segment:

                                            (3)

 

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