Which option demonstrates complementary base pairing in DNA?

Rationale

A and T demonstrate complementary base pairing in DNA.

In DNA, adenine (A) pairs specifically with thymine (T) through two hydrogen bonds, establishing a fundamental rule of base pairing that supports the double helix structure of DNA. This pairing is critical for accurate DNA replication and transcription processes.

A (A and G) YOUR ANSWER

Adenine (A) pairs with thymine (T) and does not pair with guanine (G). A and G are both purines, and the structure of DNA requires that a purine pairs with a pyrimidine to maintain uniform distance between the two strands of the double helix. Therefore, A and G do not demonstrate complementary base pairing.

B (A and C) YOUR ANSWER

Adenine (A) does not pair with cytosine (C) in DNA. C is a pyrimidine, while A is a purine, but the specific hydrogen bonding pattern dictates that A must pair with T instead. Hence, A and C do not form a complementary base pair.

C (A and A) YOUR ANSWER

Adenine (A) cannot pair with another adenine (A) because both are purines. The stability of the DNA structure relies on purines pairing with pyrimidines, which is not the case here. Thus, A and A do not exemplify complementary base pairing.

D (A and T) CORRECT

Adenine (A) pairs with thymine (T) through two hydrogen bonds, which is the standard base pairing rule in DNA. This specific pairing is essential for the structural integrity and functionality of the DNA molecule, making A and T the correct demonstration of complementary base pairing.

Conclusion

In DNA, the pairing of adenine with thymine exemplifies the principle of complementary base pairing, crucial for maintaining the double helix structure. Other combinations of bases, such as A with G, C, or A, do not fulfill this requirement, as they either involve two purines or do not match the established pairing rules. Understanding these pairing relationships is fundamental to genetics and molecular biology.

Which option demonstrates complementary base pairing in DNA?

A and T demonstrate complementary base pairing in DNA.

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