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

Hydrogen bonds between nitrogenous bases dictate base-pairing rules in the DNA double helix. The valid base pairings in DNA are:

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

Therefore, the correct base pairings are: Adenine with Thymine, and Guanine with Cytosine.

The invalid options are:

• Option (1): Adenine does not pair with Cytosine; it pairs with Thymine.
• Option (2): Thymine does not pair with Guanine; it pairs with Adenine.
• Option (4): Cytosine does not pair with Uracil. Cytosine pairs with Guanine in DNA. Uracil is present in RNA and pairs with Adenine.

Consequently, the correct selection is Option (3).