kaksiketjuja

Kaksiketjuja, often translated as "double helix," refers to a molecular structure consisting of two helical strands wound around each other. This is most famously recognized as the structure of deoxyribonucleic acid (DNA), the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses.

In the context of DNA, the two strands of the double helix are antiparallel, meaning they run in opposite directions. The strands are held together by hydrogen bonds between complementary base pairs: adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). These base pairs form the "rungs" of the DNA ladder, while the sugar-phosphate backbones form the "sides." The helical twist of the strands is a stable configuration that allows for efficient packing of the long DNA molecule within the cell nucleus.

The discovery and elucidation of the DNA double helix structure by James Watson and Francis Crick in 1953, based on crucial data from Rosalind Franklin and Maurice Wilkins, was a landmark achievement in biology. It provided a framework for understanding how genetic information is stored, replicated, and passed down through generations. This fundamental structure underpins virtually all of molecular biology and has led to advancements in genetics, medicine, and biotechnology. While DNA is the most common example, other biological molecules can also adopt double-helical forms.