Question:
In a DNA, the percentage of thymine is 20. What is the percentage of guanine in it?
In a DNA, the percentage of thymine is 20. What is the percentage of guanine in it?
Updated On: May 9, 2025
- ( 20\% )
- ( 40\% )
- ( 30\% )
- ( 60\% )
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The Correct Option is C
Solution and Explanation
According to Chargaff's rules for DNA base pairing:
The amount of adenine is always equal to the amount of thymine (T).
The amount of guanine (G) is always equal to the amount of cytosine .
The sum of the percentages of all four bases (A, T, G, C) is 100%.
Given that the percentage of thymine (T) is 20\%.
Therefore, the percentage of adenine is also 20\% (since A = T).
The combined percentage of adenine and thymine is (20\% + 20\% = 40\%).
The remaining percentage must be made up of guanine and cytosine:
Percentage of (G + C) = (100\% - 40\% = 60\%).
Since the amount of guanine (G) is equal to the amount of cytosine , the percentage of guanine is half of the combined percentage of G and C:
\[
Percentage of guanine (G) = ( \frac{60\%}{2} = 30\% ).
\]
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