Definition

1. Noun:
   • A pair of parallel helices intertwined about a common axis: This is the specific, scientific term for the structure formed by two long, thin strands that coil around each other, sharing a central axis. It is most famously the shape of the DNA molecule.

Usage

• The term "double helix" is used almost exclusively in scientific contexts, particularly in biology, genetics, and biochemistry, to describe the molecular structure of DNA.
• It functions as a singular noun. The plural form is "double helices."

Examples

• Noun:
  • The discovery of the DNA double helix was a landmark achievement in science.
  • The model clearly shows the sugar-phosphate backbones forming the sides of the double helix.
  • In a double helix, the two strands are complementary and anti-parallel.

Advanced Usage

• "The double helix": Often used with the definite article "the" to refer specifically to the structure of DNA as a general concept.
  • The double helix is an icon of modern biology.

Variants and Related Words

• Helix (noun): A three-dimensional curve that lies on a cylinder or cone, making a constant angle with the straight lines parallel to the base. A single spiral. The double helix consists of two such helices.
• Alpha helix (noun): A common secondary structure in proteins, forming a single right-handed helical coil.

Synonyms

• DNA structure: A more general term that can refer to the double helix.
• Twisted ladder: A common metaphorical description of the double helix's shape, where the sugar-phosphate chains are the "rails" and the base pairs are the "rungs."

Related Phrases/Idioms

• "To unwind the double helix": A phrase describing the separation of the two DNA strands, which occurs during processes like replication and transcription.
  • Enzymes help to unwind the double helix so its information can be read.

Noun

1. a pair of parallel helices intertwined about a common axis
   • the shape of the DNA molecule is a double helix