Question

. In a meteorite from the remains of a planet, researchers have discovered remains of the first extraterrestrial unicellular organism. Analyzing their double-stranded DNA, which was in poor condition, they found that it was made up of 32% adenine. What will be the proportion of the rest of the bases ?.

Answer 1

We can use Chargaff's rule to find the remaining compositional percentages. Adenine always pairs with thymine, so their percentages will be equal. Cytosine always pairs with guanine, so their percentages will also be equal. The sum of all four percentages must equal 100%.

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

We know that the sample is 22% adenine; this tells us it is also 22% thymine.

A=T=22%

22%+22%+C+G=100%

C+G=56%

Since cytosine and guanine are present in equal amounts, we can simply divide their sum by 2.

56%÷2=28%

C=G=28%

The final composition is 22% adenine, 22% thymine, 28% cytosine, and 28% guanine.

Uracil is only found in RNA.