The double helix describes the appearance of double-stranded DNA, which is composed of two linear strands that run opposite to each other, or anti-parallel, and twist together. Each DNA strand within the double helix is a long, linear molecule made of smaller units called nucleotides that form a chain.

What does the phrase double helix mean?

A double helix is the structure of a molecule of DNA, which takes the form of two long strands twisted together. ... The term comes from the Latin helix, or "spiral," and the fact that these molecules look like ladders twisted into a spiral.

What is on the inside of a double helix?

DNA has a double-helix structure, with sugar and phosphate on the outside of the helix, forming the sugar-phosphate backbone of the DNA. ... The phosphate backbone (indicated by the curvy lines) is on the outside, and the bases are on the inside.