Final answer:
The structure of DNA is a double helix consisting of two polynucleotide chains held together by bonds between complementary bases. Chargaff's rules can be explained by the base pairing between complementary bases. Adenine is always equal to thymine, and guanine is always equal to cytosine.
Step-by-step explanation:
The structure of DNA is a double helix consisting of two polynucleotide chains held together by bonds between complementary bases. Each nucleotide in DNA consists of a sugar (deoxyribose), a phosphate group, and one of the four bases (adenine, cytosine, guanine, or thymine).
The sugar and phosphate molecules in adjacent nucleotides form the backbone of each polynucleotide chain.
Chargaff's rules state that the amount of adenine is always equal to the amount of thymine, and the amount of guanine is always equal to the amount of cytosine. These rules can be explained by the structure of DNA. Adenine forms hydrogen bonds with thymine, and guanine forms hydrogen bonds with cytosine.
The base pairing between complementary bases allows for equal ratios of A and T, and G and C.