The basic/structural unit of a nucleic acid is

Options

A. pentose sugar
B. nucleoid
C. nucleoside
D. nucleotide

Explanation

**Step-by-Step Solution:**

1. **Understanding Nucleic Acids**: Nucleic acids, such as DNA and RNA, are essential biomolecules that store and transmit genetic information. They are composed of smaller units.

2. **Identifying the Basic Unit**: The basic structural unit of nucleic acids is known as a nucleotide. A nucleotide consists of three components: a phosphate group, a pentose sugar (which can be ribose in RNA or deoxyribose in DNA), and a nitrogenous base (which can be adenine, thymine, cytosine, or guanine).

3. **Components of a Nucleotide**:
- **Phosphate Group**: This is attached to the 5' carbon of the sugar.
- **Pentose Sugar**: This sugar is either ribose (in RNA) or deoxyribose (in DNA).
- **Nitrogenous Base**: This base is attached to the 1' carbon of the sugar and can vary among nucleotides.

4. **Formation of Polynucleotides**: When multiple nucleotides link together through phosphodiester bonds, they form a polynucleotide chain, which is the structure of DNA or RNA.

5. **Conclusion**: Therefore, the basic structural unit of nucleic acid is a nucleotide.

**Final Answer**: The basic/structural unit of a nucleic acid is a nucleotide.

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