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Karnataka Board PUCPUC Science 2nd PUC Class 12

If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA. - Biology

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Question

If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.

Numerical
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Solution

According to Chargaff’s rule, the DNA molecule should have an equal ratio of pyrimidine (cytosine and thymine) and purine (adenine and guanine). It means that the number of adenine molecules is equal to thymine molecules and the number of guanine molecules is equal to cytosine molecules.

% A = % T and % G = % C

If double stranded DNA has 20% of cytosine, then according to the law, it would have 20% of guanine.

Thus, percentage of G + C content = 40%

The remaining 60% represents both A + T molecules. Since adenine and guanine are always present in equal numbers, the percentage of adenine molecule is 30%.

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Deoxyribonucleic Acid (DNA) - Structure of Polynucleotide Chain
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Chapter 6: Molecular Basis of Inheritance - TEST YOUR PROGRESS [Page 271]

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Nootan Biology [English] Class 12 ISC
Chapter 6 Molecular Basis of Inheritance
TEST YOUR PROGRESS | Q 26. | Page 271
Nootan Biology [English] Class 12 ISC
Chapter 6 Molecular Basis of Inheritance
NCERT EXERCISES | Q 2. | Page 277
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