Question

In a DNA molecule, which of the following base-pairings is correct?

• A. Adenine pairs with Cytosine.
• B. Thymine pairs with Guanine.
• C. Adenine pairs with Thymine.
• D. Cytosine pairs with Uracil.

Hint:

Remember the base pairing rules: In DNA, A pairs with T and G pairs with C. This is known as complementary base pairing and is fundamental to the structure of the DNA molecule.

Answer 1

The Correct Option is C

In the DNA double helix, the base-pairing rules are governed by hydrogen bonds between nitrogenous bases. The correct base pairings in DNA are:

• Adenine (A) pairs with Thymine (T) through two hydrogen bonds.
• Guanine (G) pairs with Cytosine (C) through three hydrogen bonds.

Thus, the correct base pairing is: Adenine pairs with Thymine, and Guanine pairs with Cytosine.

The incorrect options are:

• Option (1): Adenine does not pair with Cytosine. Instead, Adenine pairs with Thymine.
• Option (2): Thymine does not pair with Guanine. Instead, Thymine pairs with Adenine.
• Option (4): Cytosine does not pair with Uracil. Cytosine pairs with Guanine in DNA, whereas Uracil is found in RNA, where it pairs with Adenine.

Thus, the correct answer is Option (3).