Paired DNA strands
DNA has a double helix structure. If untwisted, DNA looks like two parallel strands. Each strand has a linear sequence of A, C, G, and T. The precise order of the letters carries the coded instructions. One strand is a complementary image of the other: A always pairs with T, and C always pairs with G.
1 minute 18 seconds
Play Large: MOV / WMV (24 MB)
Play Small: MOV / WMV (7 MB)
To download the videos, in Internet Explorer right-click the link and select "Save Target As..." In Firefox right-click and select "Save Link As..." In Safari right-click and select "Download Linked File As..."