2. If 10% of the bases in a molecule of DNA are adenine, what is the ratio of adenine to guanine in the same

molecule?

A. 1:1

B. 4:1

C. 1:3

D. 1:4

Answer: Option D) 1:4

Explanation:

Recall that the sum of all nitrogenous bases in the DNA nucleotide is equal to 100%. And specific base pairings of Adenine to Thymine (A=T), and Cytosine to Guanine (C=G) must be equal.

So, the percentage of Adenine equal thymine, and that of cytosine equals guanine.

Now, A + T + C + G = 100%

So, if adenine makes up 10% of the DNA nucleotides, then thymine is also 10%.

Then, 10% + 10% + C + G = 100%

20% + C + G = 100%

C + G = 100% - 20% = 80%

Thus, divide 80% by 2 to obtain the individual percentage of cytosine and guanine. Each will take 40%

Ratio Adenine to Guanine is 10% to 40%

or 1:4 in simplest form