Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

1 Answer
Jul 2, 2016

8% will be thymine.

Explanation:

DNA is double stranded and nucleotides always appear in the same pairs:

  • cytosine pairs with guanine (G-C)
  • adenine pairs with thymine (A-T)

In this example cytosine makes up 42%, which means that guanine also makes up 42%. So 84% of the DNA is a G-C base pair.

This leaves 16% for the A-T base pair: 8% adenine and 8% thymine.