What is the basic unit of DNA, and what are the four nucleotides and their complementary base pairs?

What is the basic unit of DNA, and what are the four nucleotides and their complementary base pairs?

• A. Nucleotide; A pairs with T and C pairs with G
• B. Nucleotide; Adenine pairs with C and Guanine pairs with Thymine
• C. Carbohydrate; Adenine pairs with Guanine and Cytosine pairs with Thymine
• D. Protein; Adenine pairs with Thymine and Cytosine pairs with Guanine

Answer: (A)

DNA is built from nucleotides, the basic unit of genetic material. Each nucleotide has a deoxyribose sugar, a phosphate group, and a nitrogenous base. The four bases are adenine, thymine, cytosine, and guanine. In DNA, bases pair specifically: adenine pairs with thymine, forming two hydrogen bonds, and cytosine pairs with guanine, forming three hydrogen bonds. This complementary pairing keeps the double helix aligned and enables accurate replication and transcription. The other statements misidentify the unit (carbohydrate or protein) or propose incorrect pairings like adenine with cytosine or thymine with guanine.

DNA is built from nucleotides, the basic unit of genetic material. Each nucleotide has a deoxyribose sugar, a phosphate group, and a nitrogenous base. The four bases are adenine, thymine, cytosine, and guanine. In DNA, bases pair specifically: adenine pairs with thymine, forming two hydrogen bonds, and cytosine pairs with guanine, forming three hydrogen bonds. This complementary pairing keeps the double helix aligned and enables accurate replication and transcription. The other statements misidentify the unit (carbohydrate or protein) or propose incorrect pairings like adenine with cytosine or thymine with guanine.