Question 6

A and T

Complementary base pairing in DNA is represented by the pairing of adenine (A) with thymine (T). This specific pairing is crucial for the structure and function of DNA, ensuring accurate replication and transcription.

A) A and G

This option is incorrect as guanine (G) does not pair with adenine (A). In DNA, A pairs specifically with T, while G pairs with cytosine (C). Thus, A and G do not represent complementary base pairing.

B) A and C

Adenine (A) does not pair with cytosine (C) in DNA. Instead, A pairs with thymine (T), and C pairs with guanine (G). Therefore, A and C do not represent complementary base pairing.

C) A and A

This option is incorrect because adenine (A) cannot pair with another adenine (A) in DNA. Complementary base pairing requires specific pairs, which for A is thymine (T). Thus, A and A do not represent the proper pairing.

D) A and T

Adenine (A) pairs with thymine (T) in DNA, making this option correct. This pairing is essential for maintaining the double helix structure of DNA and for the fidelity of genetic information transfer.

Conclusion

The correct answer is D, as adenine (A) and thymine (T) represent the fundamental complementary base pairing in DNA. All other options fail to demonstrate correct pairings according to the rules of nucleotide pairing, highlighting the importance of A-T pairing in the stability and function of DNA.