Basic Composition of DNA
DNA, or deoxyribonucleic acid, is a molecule that carries genetic instructions for the development and functioning of living organisms. It is primarily made up of units called nucleotides, which are the building blocks of DNA. Each nucleotide consists of three key components: a deoxyribose sugar molecule, a phosphate group, and one of four nitrogenous bases.
Key Components of Nucleotides
The deoxyribose sugar provides the structural framework, while the phosphate group links nucleotides together to form the sugar-phosphate backbone of the DNA strand. The nitrogenous bases—adenine (A), thymine (T), cytosine (C), and guanine (G)—are attached to the sugar and are responsible for encoding genetic information through their specific pairing: A with T, and C with G.
Practical Example: Forming the DNA Strand
In a DNA strand, nucleotides link via phosphodiester bonds between the phosphate group of one nucleotide and the sugar of the next, creating a long chain. For instance, a short sequence might be A-T-C-G, where adenine pairs with thymine across complementary strands in the double helix structure discovered by Watson and Crick.
Importance in Biology
The composition of DNA enables it to store and transmit hereditary information accurately during cell division and reproduction. This structure allows for replication, where each strand serves as a template for a new complementary strand, ensuring genetic continuity across generations and facilitating processes like protein synthesis.