Sample Problem

Scientists analyze the genome of a lab mouse and discover 35% of it genome is made of adenine. What are the percentages of the other nucleotide bases? Please write the answers as whole number percentages. Do not include unnecessary decimal places.

% guanine

% thymine

% cytosine


Guanine: 15%

Thymine: 35%

Cytosine: 15%

We immediately know thymine is 35% because A and T always bond.

A: 35% + T: 35% = 70%

Entire genome: 100% - 70% = 30% for G and C

G and C must be equal because they always bond. That means,

30%/2 = 15%

Guanine and cytosine each take up 15% of the genome.