Overview of DNA
Deoxyribonucleic acid (DNA) is a molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms. Its structure is a double helix, composed of two long strands twisted around each other, with each strand made up of a backbone of sugar (deoxyribose) and phosphate groups linked by nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G). The function of DNA is to store biological information that can be replicated and used to produce proteins, which determine an organism's traits.
Key Components of DNA Structure
The double helix structure, discovered by James Watson and Francis Crick in 1953, features complementary base pairing: A pairs with T via two hydrogen bonds, and C pairs with G via three hydrogen bonds. This antiparallel arrangement allows the strands to unzip for replication. The sugar-phosphate backbone provides stability, while the bases form the rungs of the helical ladder, encoding genetic sequences in triplets called codons.
Practical Example: DNA Replication
During cell division, DNA replication occurs in the nucleus. Enzymes like helicase unwind the double helix, and DNA polymerase adds complementary nucleotides to each single strand, creating two identical DNA molecules. For instance, if one strand has the sequence ATG-CGA, the new strand will form TAC-GCT, ensuring genetic continuity in daughter cells, as seen in bacterial reproduction or human growth.
Importance and Applications of DNA
DNA's structure enables accurate replication and expression of genes, fundamental to heredity, evolution, and cellular processes like metabolism and repair. In real-world applications, understanding DNA structure supports biotechnology, such as genetic engineering for insulin production, forensic DNA profiling, and medical diagnostics for diseases like cancer, highlighting its role in advancing health and agriculture.