Question

In $DNA20\%$ bases are adenine. What percentage of bases are pyrimidines?

• A. 30 %
• B. 60 %
• C. 50 %
• D. 20 %

Answer 1

Answer: (C)

You have $20\%$ of adenine. If you have $20\%$ of adenine then you have $20\%$ of thymine, because the amount of adenine and thymine is equal.
So, Adenine $+$ Thymine $=40\%$
Therefore,the percentage of the amount of Guanine and Cytosine $=100-40\to 60\%$ i.e., $30\%$ of Guanine and $30\%$ of Cytosine, because their amounts are equal in the DNA stand. Hence the percentage of the bases of pyrimidines, i.e., Cytosine and Thymine $=30+20=$ $50\%$