Question

If an organism's dna contains 20% adenine nucleotides, what percentage of its dna is composed of guaninenucleotides? 20%

Answer 1

Let's assume that the total DNA amount = 100 %

According to Chargaff's rule, the bases pairs are highly specific. Adenine pairs up with thymine/uracil only. And, guanine pairs with cytosine only. Also, these pairs are present in equal quantities in the DNA.

If A = 20 %; then T= 20 %

Total = 20+20 = 40%

Left = 100 - 40 = 60%

Now, 60% of this DNA is guanine and cytosine. Since they are present in equal ratios, we can say that -

C = G = 30%.

Correct answer: 30%