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Structure of Nucleic Acid5

Structure of Nucleic Acid5 - runs in the 3 to 5 direction...

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Structure of Nucleic Acids Nucleic Acids Nucleotides join together through phosphodiester linkages between the 5' and 3' carbon atoms to form nucleic acids. The 3' -OH of the sugar group forms a bond with one of the negatively charged oxygens of the phosphate group attached to the 5' carbon of another sugar. When many of these nucleotide subunits combine, the result is the large single-stranded polynucleotide or nucleic acid, DNA () Figure %: The Nucleic Acid DNA If you look closely, you can see that the two sides of the nucleic acid strand shown above are different, resulting in polarity. At one end of the large molecule, the carbon group is unbound and at the other end, the -OH is unbound. These different ends are called the 5'- and 3'-ends, respectively. The Helical Structure of DNA shows a single strand of DNA. However, as stated earlier, DNA exists as a double-helix, meaning two strands of DNA bind together.
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Figure %: Double-helical DNA As seen above, one strand is oriented in the 5' to 3' direction while the complementary strand
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Unformatted text preview: runs in the 3' to 5' direction. Because the two strands are oppositely oriented, they are said to be anti-parallel to each other. The two strands bond through their nitrogen bases (marked A, C, G, or T for adenine, cytosine, and guanine). Note that adenine only bonds with thymine, and cytosine only bonds with guanine. The nitrogen bases are held together by hydrogen bonds: adenine and thymine form two hydrogen bonds; cytosine and guanine form three hydrogen bonds. An important thing to remember about the structure of the DNA helix is that as a result of anti-parallel pairing, the nitrogen base groups face the inside of the helix while the sugar and phosphate groups face outward. The sugar and phosphate groups in the helix therefore make up the phosphate backbone of DNA. The backbone is highly negatively charged as a result of the phosphate groups....
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