What does a double helix in DNA is held together by?
First off - it is important to understand that a nucleotide (the monomer of DNA) is composed of 3 things: a sugar, a phosphate group, and a nitrogenous base. Next - understand that the "backbone" of DNA is composed of the sugars and phosphates.
That leaves you with nitrogenous bases. Hydrogen bonds form between the nitrogenous bases off opposite strands in the double helix. THIS is what holds the double helix together.
In molecular biology, the term double helix refers to the structure formed by double-stranded molecules of nucleic acids such as DNA and RNA. The double helical structure of a nucleic acid complex arises as a consequence of its secondary structure, and is a fundamental component in determining its tertiary structure. The term entered popular culture with the publication in 1968 of The Double Helix: A Personal Account of the Discovery of the Structure of DNA…