Answer:
13% cytosine
37% thymine
Explanation:
There are two types of nucleotides based on their structures - purines and pyrimidines.
The purines are adenine and guanine. The pyrimidines are thymine and cytosine.
Chargaff's rule states that the ratio of purines to pyrimidines in a molecule of DNA is 1:1
Therefore, the total number of A+G is the same at the total number of C+T.
All 4 bases together must equal 100% of the DNA molecule
If there is 13% guanine, and guanine always pairs with cytosine, there is also 13% cytosine.Together, that is 26% of the total sample.
100-26 = 74% of the total of adenine and thymine.
Since there are equal amounts of A and T, we know that the DNA sample is 74/2 = 37% thymine
