The basic unit of nucleic acid is
nucleotide
Nucleic Acid Basic Unit: Understanding the Building Blocks
Nucleic acids are essential macromolecules in biology, primarily known for storing and transmitting genetic information. The two main types are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Like other polymers such as proteins (made of amino acids) or polysaccharides (made of monosaccharides), nucleic acids are also made up of repeating smaller units.
The question asks for the basic unit of nucleic acid. Let's look at the options provided.
What is a Nucleotide?
A nucleotide is the fundamental building block of nucleic acids. Each nucleotide is composed of three parts:
- A phosphate group
- A pentose sugar (deoxyribose in DNA, ribose in RNA)
- A nitrogenous base (Adenine, Guanine, Cytosine, Thymine in DNA; Adenine, Guanine, Cytosine, Uracil in RNA)
These nucleotides link together through phosphodiester bonds between the phosphate group of one nucleotide and the sugar of the next, forming the long chains of DNA and RNA.
What is a Nucleoside?
A nucleoside is similar to a nucleotide but lacks the phosphate group. It consists only of:
- A pentose sugar (deoxyribose or ribose)
- A nitrogenous base (Adenine, Guanine, Cytosine, Thymine, or Uracil)
Therefore, a nucleoside is a part of a nucleotide but not the complete repeating unit that forms the nucleic acid polymer.
What is a Nucleoid?
The nucleoid is a region within prokaryotic cells (like bacteria) where the genetic material, typically a circular DNA molecule, is located. It is not a molecule or a building block, but rather a cellular structure or region.
Comparing Nucleotide and Nucleoside
Here is a simple comparison of the components:
| Component | Nucleotide | Nucleoside |
|---|---|---|
| Phosphate group | Present | Absent |
| Pentose sugar | Present | Present |
| Nitrogenous base | Present | Present |
Conclusion: Identifying the Basic Unit of Nucleic Acid
Since nucleotides are the units that link together via phosphodiester bonds to form the polymer chain of DNA or RNA, they are considered the basic repeating unit or monomer of nucleic acids.
Based on the composition and how the nucleic acid chain is assembled, the nucleotide is the correct basic unit.
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