6 - Nucleic Acids

6 - Nucleic Acids - 580.221 Lecture 6(Nucleic Acids Fall...

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580.221- Lecture 6 (Nucleic Acids) Fall 2008 1 Nucleic Acids The genetic code Eileen Haase Fall 2008–Lecture #6 1 What do nucleic acids do? Nucleic acids are arranged into genes –the hereditary units of an organism Genes are copied millions of times during the life of a multicellular organism Genes primarily contain the information needed to make proteins Enzymes (catalyze all the cell’s reactions) Regulate gene expression Enable cells and entire organisms to move Communication–with in a cell and between cells 2 How Genes Influence Traits Genes specify the amino acid sequence of proteins The amino acid sequence determines the shape and activity of proteins Proteins determine in large measure what the body looks like and how it functions Mutations in a gene result in alleles (alternative forms of a gene) This ultimately leads to a change in the amino acid sequence and, hence, activity of the protein Natural selection may favor one allele over another 3 Turning Genes Off and On Genes are typically controlled at the level of transcription In prokaryotes, proteins either block or allow the RNA polymerase access to the promoter Repressor block the promote Repressors block the promoter Activators make the promoter more accessible Most genes are turned off except when needed 4 Watson and Crick determined the structure of DNA in 1953. Understanding the structure showed how DNA could be replicated: Structure = function The structure of DNA led to an understanding of the function of DNA in providing almost unlimited, accurate copies of the genetic code 5 Central Dogma of Molecular Biology DNA >RNA >protein 6
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580.221- Lecture 6 (Nucleic Acids) Fall 2008 2 Rules for Protein & Nucleic Acid Synthesis There are a limited number of different monomeric building blocks. Monomers are added one at a time. Each chain has a specific starting point. Growth proceeds in one direction. There is a fixed and specific terminus (‘stop’). The primary synthetic product is often modified. 7 Two types of nucleic acids DNA–conta ins all the information to build all the different cells and tissues Initially thought to be much too simple a molecule (only 4 different subunits) RNA–protein synthesis mRNA (messenger) tRNA (transfer) rRNA (ribosomal) 8 Genome–a complete set of genes Typical human cell has 1 meter of DNA (3 x 10 9 nucleotides) The linear sequence of nucleotides in a gene spells out the linear (primary) sequence of amino acids in a protein Parts of DNA are regulatory regions 9 Structure of nucleic acids DNA and RNA are polymers of four types of nucleotides subunits Each nucleotide has a Sugar 5 Carbon; ribose or deoxyribose A Phosphate group And a Base Adenine Guanine Cytosine Thymine/Uracil 10 C5’ The five carbons in the sugar are numbered, C1’ is attached to the C1’ C2’ C3’ C4’ attached to the base.
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6 - Nucleic Acids - 580.221 Lecture 6(Nucleic Acids Fall...

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