Question

which of the following statements correctly describes one of chargaffs rules regarding dna?
dna has a double helical structure.
the percentages of adenine and thymine are roughly equal, as are the percentages of guanine and cytosine in the dna of a given species.
the percentages of adenine and cytosine are roughly equal, as are the percentages of guanine and thymine in the dna of a given species.
dna base composition does not vary between species.

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) for a given species. The double - helical structure of DNA was proposed by Watson and Crick, not related to Chargaff's rules. Also, DNA base composition varies between species.

Answer:

The percentages of adenine and thymine are roughly equal, as are the percentages of guanine and cytosine in the DNA of a given species.