Question

Which of the following is an example of correct DNA base pairing?

A. Adenine and uracil
B. Guanine and cytosine
C. Thymine and uracil
D. Guanine and thymine

Answer 1

The correct answer is B.

The base pairing interactions in DNA are:
A-T
G-C

Answer A is a correct pair but not for DNA, since uracil is one of the bases in RNA.

Answer 2

B. Guanine and cytosine is the example of correct DNA base pairing, according to the complementarity rules where adenine pairs with thymine, and cytosine pairs with guanine.

Step-by-step explanation:

The correct example of DNA base pairing is B. Guanine and cytosine. In DNA, a purine base always pairs with a pyrimidine base. This follows Chargaff's rule where adenine (a purine) pairs with thymine (a pyrimidine), and cytosine (a pyrimidine) pairs with guanine (a purine). Adenine and thymine are held together by two hydrogen bonds, while cytosine and guanine are held together by three hydrogen bonds. Both pairings are essential for the consistent structure of the DNA double helix.