What are the nitrogenous bases found in DNA?

• A. A, T, C, U
• B. A, T, C, G
• C. A, C, G, T
• D. A, U, G, C

Answer: (B)

In DNA, the nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G). These bases are vital for the encoding of genetic information. Adenine pairs with thymine, and cytosine pairs with guanine, forming the rungs of the DNA double helix structure through base pairing.

The presence of uracil (U) in option A and option D indicates that those choices refer to RNA rather than DNA, as uracil replaces thymine in RNA. Thus, options A and D do not accurately represent the nitrogenous bases found in DNA. The question specifically pertains to DNA, which clearly identifies option B as the correct answer.

Option C includes the same bases but presents them in a different order; however, it omits thymine and does not correspond correctly to the classification of nitrogenous bases specifically in DNA, making it incorrect as well. Therefore, the correct identification of the bases in DNA as adenine, thymine, cytosine, and guanine is established in option B.