AP BIOLOGY

Detailed explanation-1: -Under normal circumstances, the nitrogen-containing bases adenine (A) and thymine (T) pair together, and cytosine (C) and guanine (G) pair together. The binding of these base pairs forms the structure of DNA .

Detailed explanation-2: -Adenine always pairs with thymine through two hydrogen bonds in DNA. Similarly, adenine pairs with uracil through two hydrogen bonds in RNA and guanine always pairs with cytosine through three hydrogen bonds in both the nucleic acids.

Detailed explanation-3: -In RNA, uracil pairs with adenine. In a DNA molecule, the nucleotide thymine (T) is used in place of uracil.

Detailed explanation-4: -Complementary Sequence: Since DNA has two strands, every DNA sequence has a complementary sequence running parallel. In the complementary sequence, Adenine (A) is always paired with Thymine (T), and Cytosine (C) is always paired with Guanine (G).

Detailed explanation-5: -Adenine always bonds with thymine, making them DNA’s other pair of complementary bases. These pairs form the “rungs” of the DNA ladder.