Knowledge of where the H's are is important in assessing the hydrogen bonding characteristic of a base pair. Compare the structure above with that at right.Ĭonsequently, chemists and biologists who look at these structures have to figure out where the hydrogens are placed based on their knowledge of chemistry. Note that in DNA crystal structures, hydrogens (H) are not detected ( why?) and so are not shown in the structure at right. An example is the base pair between cytosine (C) and guanosine (G): This is important, since the order of the nucleotides contains information, in much the same way that the order of 0's and 1's on a computer tape contains information.īase Pairing Complementary refers to the way two individual bases can interact in a "lock and key" fashion. In contrast, nature's polymer, DNA, is put together with extreme precision. Most chemical polymers are a distribution of lengths and compositions. The "unit" in this case can be any one of four nucleotides. The units are connected together via phosphate linkages In the simple world of textbooks, the base pairs are completely "co-planar." In the real world, small, but significant forces act to distort the base pairs slightly, to achieve a real-world energy minimum.ĭNA is a polymerA is any chemical species made up of repeating units. In fact, it is the textbooks which are unusual. Real DNAThose of you who have seen textbook pictures of DNA might notice something unusual about this DNA. Together these serve as the backbone of DNA. The sugar rings are connected by phosphate linkages. NucleotideA nucleotide is composed of 3 parts: The stick representation above is the actual structure of a very short stretch of DNA But other forces are important in maintaining the structure. The shape and hydrogen bonding between bases ensures complementarity and their planarity allow them to "stack" on each other. Complementary strands of DNA have nucleotides which interact favorably via base pairing. Each strand of DNA is made of repeating units, called nucleotides. The structure at right, B-Form duplex DNA, contains two interacting molecules: two complementary strands of DNA.ĭuplex DNA is a long polymeric species made up of two individual molecules. Click on the "?" in the menu above for more tips on manipulating the molecule at right.Ĭlick "reset" above, to return the view to the starting point. If you "click and drag" in the window at right, you can rotate the molecule yourself. Read the text and on buttons or highlighted words. B-Form DNAThis is an interactive tutorial on DNA. This site requires that JavaScript (and JAVA) be enabled in your browser.
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