Nucleic AcidPrint

Nucleic AcidPrint - Nucleic Acid Everyone has heard of DNA....

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Everyone has heard of DNA. But can you explain what DNA is exactly? DNA is a member of a group of marcomolecules called nucleic acids . Nucleic acids have a specialized and important role in maintaining and carrying genetic information. Segments of DNA called genes tell the cell how to build all the different types of proteins found in a cell. And these proteins, of course, work with lipid and carbohydrate marcomolecules in the cell to generate energy and form cellular structures. Like proteins, carbohydrates, and lipids, nucleic acids are polymers made by linking individual monomers together. In the case of DNA, and another familiar nucleic acid, RNA, the monomer is a nucleotide . Usefully, the molecule group that DNA and RNA belong to is spelled out in their expanded names. DNA is short for deoxyribo nucleic acid and RNA is short for ribo nucleic acid . Nucleotides, the basic unit of all nucleic acids, are composed of three main parts; a sugar, a phosphate group, and a nitrogen base (see figure 1). Nucleic Acid
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1. The sugar group is a 5 carbon ring (or pentose). The labeling of the carbons (1', 2', 3', 4' and 5') describes their location with respect to the central oxygen (O) in the ring. Of note is the hydroxyl group (-OH) attached to the 3' carbon. In DNA the sugar group is deoxyribose while in RNA it is ribose. The difference between the two pentoses is that deoxyribose contains a hydrogen (-H) at the 2' carbon position while ribose contains a hydroxyl group (-OH) at the 2' carbon position. Functionally, the hydroxyl group in the ribose sugar is a site for hydrolysis, which makes RNA much less stable than DNA. What kind of sugar is shown in figure 1? 2. The phosphate group attached to the sugar at the 5' carbon is key for linking nucleotides together to form nucleic acids. The phosphate group on one nucleotide reacts with the 3' carbon -OH group on another nucleotide creating a chemical bond that links adjacent nucleotides together. This type of bond is called a phosphodiester bond . Entire chains of DNA and RNA are built by linking nucleotides together one by one. This reaction normally does not occur spontaneously and must be catalyzed by enzymes called polymerases . DNA polymerase makes DNA and RNA polymerase makes RNA. 3. The nitrogen base is bound to the sugar group at the 1' carbon, and in DNA nucleotides there are 4 different types of nitrogen bases; cytosine, thymine, adenine, and guanine. These 4 bases are broken up into two groups on the basis of their structure. The pyrimidines, cytosine and thymine, are composed of a single ring while the purines, adenine and guanine, have double rings (See figure 2). Generally, a nucleotide is
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Nucleic AcidPrint - Nucleic Acid Everyone has heard of DNA....

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