Question

DNA is

• A. Monomer of deoxyribonucleotides
• B. Polymer of deoxyribonucleotides
• C. Monomer of ribonucleotides
• D. Polymer of ribonucleotides

Hint:

DNA is a Polymer of Deoxyribonucleotides (Sugar: 2'-deoxyribose; Bases: A, T, G, C).
RNA is a Polymer of Ribonucleotides (Sugar: D-ribose; Bases: A, U, G, C).
Single nucleotide units are monomers, whereas complete nucleic acid strands are polymers.

Answer 1

The Correct Option is B

Concept:
Deoxyribonucleic acid (DNA) represents the principal chemical entity that stores and transmits hereditary information in nearly all cellular life forms.
It consists of long macromolecular chains constructed from individual building blocks that carry specific sequences of nitrogenous bases.
Understanding whether DNA exists as a singular building unit (monomer) or as a repetitive macromolecular chain (polymer) is fundamental to molecular genetics and cell biology.
Furthermore, distinguishing between deoxyribose-based and ribose-based nucleic acids defines the difference between DNA and RNA.

Step 1: Understanding the Basic Subunits of DNA:
The fundamental monomeric repeating unit of DNA is a deoxyribonucleotide.
Each deoxyribonucleotide is composed of three distinct chemical parts: a heterocyclic nitrogenous base (adenine, guanine, cytosine, or thymine), a 2'-deoxy-D-ribose pentose sugar, and a phosphate group esterified to the 5' carbon of the sugar.

Step 2: Mechanism of Chain Formation (Polymerization):
Multiple deoxyribonucleotides undergo condensation polymerization within the cell nucleus or nucleoid region.
During this polymerization, strong covalent bonds called 3',5'-phosphodiester linkages are formed between the 3'-hydroxyl ($-\text{OH}$) group of one nucleotide's deoxyribose and the 5'-phosphate group of the succeeding nucleotide.
This repetitive linkage creates an unbranched, high-molecular-weight structural backbone consisting of alternating sugar and phosphate units.

Step 3: Comparison with Ribonucleotides:
Ribonucleotides contain ribose sugar (with a hydroxyl group at the 2' carbon position) and uracil in place of thymine, which polymerize to form Ribonucleic Acid (RNA).
Since DNA contains deoxyribose sugar and consists of thousands to millions of these joined units, it is classified strictly as a polynucleotide or polymer of deoxyribonucleotides.

Step 4: Final Answer:
Therefore, DNA is a polymer of deoxyribonucleotides, making (B) the correct option.