The Double Helix

The most unique and interesting aspect of DNA is its three dimensional helical structure, the double helix. The double helix consists of two strands of complementary DNA running antiparallel, that is, 5' to 3' on one strand, and 3' to 5' on the other strand.

The primary structure of an example sequence of double-stranded DNA is given below. Notice how every guanine is matched with a cytosine and every adenine is matched with a thymine.

The same sequence of double-stranded DNA is shown below with the backbone (sugars and phosphates) in purple, the bases color-coded as above, and hydrogen bonds in cyan.


Backbone

Bases

H-Bonds

Spacefill

Highlight Strands

 

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