Chapter 16: How Genes Work [MIDTERM 2 MATERIAL]

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Mark Huyler

How Genes Work Genes "contain instructions for making proteins" DNA "is only an information-storage molecule" Gene Expression "the process of converting archived information into molecules that actually do things in the cell" The One-Gene, One-Enzyme Hypothesis "Each genes contains the information needed to make an enzyme" George Beadle Edward Tatum The One-Gene, One-Enzyme Hypothesis N.Crassa Pyridoxine, B6 vitamin Radiation Mutants "Made genes defective to see its phenotypic results" Knock-out "null, loss of function" alleles The Experiment of One-Gene, One Enzyme Adrian Srb Norman Horowitz Metabolic Pathway Arginine Production Different genes lead to the synthesis of each enzyme Precursor -> X -> Y -> Arginine N.Crassa Need Arginine to grow Arginine Radiation Genetic Screen "picking certain mutants out of randomly generated mutants" mutant categories: arg1, arg2, arg3 Francis Crick The Central Dogma The Genetic Code Hypothesis The Central Dogma "The flow of information in cells" DNA --> RNA --> Proteins Genotype Phenotype DNA --> RNA --> Proteins "DNA codes for RNA, which codes for proteins" 20 amino acids Coding Region Gene Primary sequence of amino acids in proteins The Central Dogma: Genotype vs. Phenotype Genotype "Determined by the sequence of bases in its DNA" Phenotype "Product of the proteins it produces" Alleles of a gene differ in their DNA sequence Proteins produced by different alleles -> different amino acid sequence --> different function --> different phenotype "A difference in even one amino acid can go a long way" Exceptions to the Central Dogma Many genes code for RNA molecules that do not function as mRNA -- They are not translated into proteins, may perform important functions for cell instead. In some cases, information flows from RNA back to DNA Virus "have genes consisting of RNA" Viral Polymerase Reverse Transcriptase "synthesizes DNA from RNA" Human Immunodeficiency Virus (HIV) AIDS "uses RNA virus and reverse transcriptase" Poisoning of HIV reverse transcriptase The Genetic Code "The rules that specify the r
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