Question

In DNA, adenine pairs with.

• A. Guanine
• B. Thymine
• C. Cytosine
• D. Uracil

Answer 1

The correct option is B

Thymine

The correct option is B.

Explanation of the correct option:

Option B:

1. Adenine is a nitrogenous base found in the DNA nucleotide.
2. It is a purine base.
3. It has two heterocyclic rings.
4. It is called a nitrogenous base, as it has nitrogen and it is a base.
5. It binds to thymine using hydrogen bonds.
6. The A-T and G-C pairing follow the chargaff's rule.
7. According to the chargaff rule the ratio of the number of purines (adenine, guanine) is always equal to the number of pyramides (cytosine, uracil, and thymine) in a DNA helix.
8. Hence, an equal number of adenine pairs with an equal number of thymine via two double bonds.

Explanation of the incorrect options:

Option A:

1. Guanine is a nitrogenous base.
2. It binds to cytosine via three hydrogen bonds in the DNA nucleotides to form the helix.
3. It is a purine base.
4. It does not pair with adenine.

Option C:

1. Cytosine is a pyrimidine base.
2. It has a single heterocyclic ring.
3. It pairs with the purine guanine in the DNA (Deoxyribonucleic acid) helix through three hydrogen bonds.

Option D:

1. Uracil is a pyrimidine base.
2. It also has one heterocyclic ring.
3. It is not found in the DNA nucleotides.
4. It pairs with the adenine in an RNA (ribonucleic acid) molecule.

Final answer: In DNA, adenine pairs with thymine.