Question

Which of these is not a nitrogenous base?

• A. Adenine
• B. Cytokinin
• C. Guanine
• D. Thymine

Answer 1

The correct option is B

Cytokinin

The correct option is B.

Explanation of correct option:

1. Nitrogenous bases also called nucleobases are nitrogen-containing biological compounds, which produce nucleosides that in turn are the constituents of nucleotides.
2. The tendency of nitrogen bases to produce base pairs and to heap one upon another directly results in the formation of long-chain helical compositions like DNA. (deoxyribonucleic acid) and RNA (ribonucleic acid).
3. A plant hormone, which influences growth and stimulation of cell division is cytokinin.
4. It is synthesized in the roots and is generally obtained from adenine.
5. The hormone cytokinin regulates leaf primordial number, shoot meristem size, and shoot and leaf growth.
6. Cytokinin is a plant hormone, not a nitrogenous base.

Explanation of incorrect options:

Option A:

1. In the DNA, adenine is one of the four nucleotide bases, it is a purine.
2. In the double-stranded DNA molecule, adenine on one strand pairs with thymine on the contrary strand.

Option C:

1. In the DNA, guanine is one of the four nucleotide bases, it is a purine.
2. In the double-stranded DNA molecule, guanine on one strand pairs with cytosine on the contrary strand.

Option D:

1. Thymine, a pyrimidine, is one of the four nucleotide bases found in DNA.
2. Thymine on one strand of the double-stranded DNA molecule pairs with adenine on the opposing strand.

Final answer: Cytokinin is not a nitrogenous base.