If you were to zoom into a cell and look past the membranes and organelles, you would eventually find the blueprint of life: DNA. But DNA is not a single, monolithic substance; it is a massive polymer constructed from smaller, repeating units. These fundamental units are called nucleotides. Every piece of genetic information, whether in the form of DNA or RNA, is built by stringing these specific molecules together.
To understand how genetic information is stored and copied, we must first master the anatomy of a single nucleotide. A nucleotide is composed of three distinct chemical components: a nitrogenous base, a pentose sugar, and a phosphate group.
The Nitrogenous Base: The Genetic Code
The most critical part of the nucleotide regarding "information" is the nitrogenous base. These are nitrogen-containing organic molecules that act as the "letters" in the genetic alphabet. Depending on the specific arrangement of atoms in these bases, they carry different chemical identities that allow them to pair specifically with other bases.
Nitrogenous bases are categorized into two main groups based on their chemical structure:
- Purines: These consist of a double-ring structure (a six-membered ring fused to a five-membered ring). The two primary purines are Adenine (A) and Guanine (G).
- Pyrimidines: These consist of a single six-membered ring. The primary pyrimidines are Cytosine (C), Thymine (T) — found in DNA — and Uracil (U) — found in RNA.
Keep reading for free.
Create an account to finish this reading and make it part of your study routine.
Continue reading freeAlready have an account? Log in
Updated