DNA is unique because the order, or sequence, of its component molecules varies from organism to organism. Although all DNA is composed of the same building blocks, the precise arrangement of these blocks is what distinguishes one individual from another.
Understanding DNA Uniqueness
While the fundamental components of DNA (nitrogenous bases, deoxyribose sugar, and phosphate group) are the same across all organisms, the uniqueness lies in how these components are arranged.
The Common Building Blocks
All DNA molecules are built from the same four nitrogenous bases:
| Base | Type |
|---|---|
| Adenine | Purine |
| Guanine | Purine |
| Cytosine | Pyrimidine |
| Thymine | Pyrimidine |
The Key to Uniqueness: Sequence
The sequence of these bases along the DNA molecule determines the genetic information. The reference states: "It is simply the order in which these smaller molecules are arranged that differs among individuals." Think of it like the letters of an alphabet. The alphabet is the same for everyone, but the order in which we arrange the letters creates unique words and sentences.
Analogy: A Book
Imagine DNA as a book.
- The Pages (DNA strands): All books use pages.
- The Letters (Nitrogenous bases): All books use letters of the alphabet.
- The Sentences (Gene sequences): The order of the letters creates unique sentences.
- The Story (Genetic information): The entire sequence of sentences tells a unique story, defining the characteristics of an organism.
Example: Human vs. Chimpanzee DNA
Humans and chimpanzees share a high degree of DNA similarity. However, the slight differences in the sequence of their DNA bases result in significant differences in their physical and behavioral traits. Even seemingly small changes in the arrangement of these bases can have profound effects.
