Deoxyribonucleic acid, commonly known as DNA, is the molecule that carries genetic information in most organisms. It is structured in a specific way that allows it to store and transmit this vital data.
The Structure of DNA: A Double Helix
The fundamental structure of DNA is described as a double helix. This means that DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix. This shape is crucial for its function, allowing the molecule to be both stable and capable of replication.
Key Components of a DNA Strand
Each of the two linked strands in the double helix has a specific composition:
- Backbone: Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. These components form the sides of the "twisted ladder," providing structural support.
- Bases: Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G) or thymine (T). These bases are like the "rungs" of the ladder, connecting the two strands across the center.
The Four DNA Bases
The four bases found in DNA are:
| Base Name | Symbol |
|---|---|
| Adenine | A |
| Cytosine | C |
| Guanine | G |
| Thymine | T |
These bases pair up in a specific way across the double helix: Adenine (A) always pairs with Thymine (T), and Cytosine (C) always pairs with Guanine (G). This specific pairing rule is essential for how DNA replicates and how genetic information is encoded.
DNA's Role
While the structure is key, the arrangement of these bases along the strand forms a sequence that spells out the genetic instructions for building and operating an organism. This sequence is unique for almost every living being.
In summary, DNA is characterized by its iconic double helix structure, built from sugar-phosphate backbones and specific pairings of the four nitrogenous bases (A, T, C, G), forming the blueprint of life.
