How is DNA structured?

DNA is structured as a double helix, composed of two strands of nucleotides twisted around each other.

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms. Its structure is often compared to a twisted ladder, known as a double helix. This double helix structure was first discovered by scientists James Watson and Francis Crick in 1953.

The 'rungs' of the DNA ladder are made up of pairs of four types of molecules called nucleotides: adenine (A), thymine (T), guanine (G), and cytosine (C). These nucleotides pair up in a specific way: A always pairs with T, and G always pairs with C. This is known as base pairing and is crucial for DNA replication.

The 'sides' of the ladder are made up of alternating sugar (deoxyribose) and phosphate molecules. These form the backbone of the DNA structure, holding the nucleotides in place. The sugar and phosphate molecules are connected by covalent bonds, which are strong and stable, ensuring the DNA molecule can withstand the chemical reactions that occur within cells.

The double helix structure of DNA is also important for its function. The twisting of the two strands around each other allows the DNA to be compacted into the tiny space of a cell nucleus. Additionally, the double helix can 'unzip' down the middle, allowing each strand to act as a template for the creation of a new, identical strand. This is how DNA replicates itself, ensuring that each new cell has a complete set of genetic instructions.

In summary, the structure of DNA as a double helix, with its specific base pairing and sugar-phosphate backbone, is fundamental to its role as the carrier of genetic information in all living organisms.