Thirty percent of the bases in a sample of DNA extracted from eukaryotic cells is adenine. What percentage of cytosine is present in this DNA?

Question

Thirty percent of the bases in a sample of DNA extracted from eukaryotic cells is adenine. What percentage of cytosine is present in this DNA? (A) 10% (B) 20% (C) 30% (D) 40%

Tardigrade Admin · Accepted Answer

If 30 percent of DNA is adenine, then by Chargaff's rule 30 percent will be thymine. The remaining 40 percent of the DNA is cytosine and guanine. Since the ratio of cytosine to guanine must be equal, then each accounts for 20 percent of the bases.

Q. Thirty percent of the bases in a sample of DNA extracted from eukaryotic cells is adenine. What percentage of cytosine is present in this DNA?

10%

20%

30%

40%

If $30$ percent of DNA is adenine, then by Chargaff's rule $30$ percent will be thymine. The remaining $40$ percent of the DNA is cytosine and guanine. Since the ratio of cytosine to guanine must be equal, then each accounts for $20$ percent of the bases.