Question

what did chargaff discover while studying bases in the dna of organisms?
the bases in the dna of each organism were unique.
the ratios of thymine and adenine were similar, as were the ratios of guanine and cytosine.
the overall percentages of bases were different from one organism to the next.
there were equal amounts of all four bases in every organism, or 25 percent of each base.

Explanation:

Chargaff's rules state that in DNA, the amount of adenine (A) is equal to thymine (T), and the amount of guanine (G) is equal to cytosine (C). This means the ratios of thymine and adenine are similar (since \(A = T\)), and the ratios of guanine and cytosine are similar (since \(G=C\)). The first option is incorrect because DNA bases follow base - pairing rules (not unique in that sense). The third option is not the key discovery (the key was base - pairing ratios). The fourth option is wrong as \(A = T\), \(G = C\) but \(A+T
eq G + C\) in most cases.

Answer:

The ratios of thymine and adenine were similar, as were the ratios of guanine and cytosine.