A double-stranded DNA molecule is separated into its constituent strands, and the strands are separated in an ultracentrifuge. In one of the strands the base composition is 22% A, 30% T, 20% G, and 28% C. What is the base composition of the other strand?

22% T, 30% A, 20% C, and 28% G

Explanation:

Two strands of double-stranded DNA molecules are held together by hydrogen bonds formed between the complementary bases. Adenine and thymine are bonded together by two hydrogen bonds. Similarly, cytosine and guanine form a base pair. Therefore, if one strand of a double helix DNA has 22% A, 30% T, 20% G, and 28% C, the other strand would have the following composition:

22% A: 22% T

30% T: 30% A

20% G: 20% C

28% C: 28% G

This is also called the Chargaff rule.