stars and stripes 2 italics the national anthem of the united states of america based on a poem written by francis scott key on september 14 1814 and set by him to the melody of the english song to anacreon in heaven officially adopted by the u s congress in 1931 examples from the web for star spangled banner expand
The two strands of DNA are held together by weak hydrogen bonds (remember, something must hold them together!) between the nitrogenous bases. The interesting (and very important) aspect of the Watson-Crick model is that these hydrogen bonds are base specific.
Complementary base pairing describes the manner in which the nitrogenous bases of the DNA molecules align with each other. Complementary base pairings are also responsible for the double-helix structure of DNA. If you imagine yourself looking at a closet with four pairs of shoes that are all mixed up, complementary base pairing would be the set of rules that you would use to know which shoes go together.