Nucleic Acids

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  • Topic: DNA, RNA, Pyrimidine
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  • Published : January 27, 2013
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Chapter 4: Nucleic Acids and the RNA World

1. 4.1 – What is a Nucleic Acid?
* Nucleic acids are made up of monomers called nucleotides * Three components of a nucleotide:
1. Phosphate group—attached to the 5’ carbon
2. Sugar – carbonyl group and several hydroxyl groups
3. Nitrogenous base
* The prime (‘) symbols indicate the carbon being is part of the sugar—not attached to the nitrogenous base. * Four different nucleotides, each of which contains a different nitrogenous base 1. Purines—adenine (A), guanine (G)

2. Pyrimidines—cytosine (C), uracil (U); T for DNA

A. How Do Nucleotides Polymerize to form Nucleic Acids?
i. The polymerization reactions involve the formation of a bond between the phosphate group of one nucleotide and the hydroxyl group of the sugar components phosphodiester linkage ii. When the nucleotides involved contain the sugar ribose, they polymer that is produced is ribonucleic acid (RNA) iii. DNA and RNA strands are directional

iv. The sugar phosphate backbone of a nucleic acid is directional, as in the peptide-bonded backbone of a polypeptide. v. In a strand of RNA or DNA, one end has an unlinked 5’ carbon while the other has an unlinked 3’ carbon—meaning a carbon that is not linked to another nucleotide. 5’ 3’ direction. vi. The sequence of nitrogenous bases forms the primary structure of a molecule, analogous to the sequence of amino acids.

2. 4.2 – DNA Structure and Function
* The primary structure of nucleic acids is somewhat similar to the primary structure of proteins; Proteins have a peptide-bonded backbone with a series of R-groups. * DNA and RNA molecules have a sugar phosphate backbone, created by phosphodiester linkages, and a sequence of any 4 nitrogenous bases. * The secondary structure of nucleic acids is formed by H-bond between nitrogenous bases.

A. What is the Nature of DNA’s secondary structure?
i. (1) The # of purines in a given DNA...
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