This chapter describe the contributions made by Garrod, Beadle, and Tatum to our understanding of the relationship between genes and enzymes; briefly explain how information flows from gene to protein; compare transcription and translation in bacteria and eukaryotes; explain what it means to say that the genetic code is redundant and unambiguous;. | Chapter 17 From Gene to Protein Overview: The Flow of Genetic Information The information content of DNA Is in the form of specific sequences of nucleotides along the DNA strands The DNA inherited by an organism Leads to specific traits by dictating the synthesis of proteins The process by which DNA directs protein synthesis, gene expression Includes two stages, called transcription and translation The ribosome Is part of the cellular machinery for translation, polypeptide synthesis Figure Concept : Genes specify proteins via transcription and translation Evidence from the Study of Metabolic Defects In 1909, British physician Archibald Garrod Was the first to suggest that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell Nutritional Mutants in Neurospora: Scientific Inquiry Beadle and Tatum causes bread mold to mutate with X-rays Creating mutants that could not survive on minimal medium Using genetic crosses They determined that their mutants fell into three classes, each mutated in a different gene Figure Working with the mold Neurospora crassa, George Beadle and Edward Tatum had isolated mutants requiring arginine in their growth medium and had shown genetically that these mutants fell into three classes, each defective in a different gene. From other considerations, they suspected that the metabolic pathway of arginine biosynthesis included the precursors ornithine and citrulline. Their most famous experiment, shown here, tested both their one gene–one enzyme hypothesis and their postulated arginine pathway. In this experiment, they grew their three classes of mutants under the four different conditions shown in the Results section below. The wild-type strain required only the minimal medium for growth. The three classes of mutants had different growth requirements EXPERIMENT RESULTS Class I Mutants Class II Mutants Class III Mutants Wild type Minimal medium (MM) (control) MM + Ornithine MM + Citrulline | Chapter 17 From Gene to Protein Overview: The Flow of Genetic Information The information content of DNA Is in the form of specific sequences of nucleotides along the DNA strands The DNA inherited by an organism Leads to specific traits by dictating the synthesis of proteins The process by which DNA directs protein synthesis, gene expression Includes two stages, called transcription and translation The ribosome Is part of the cellular machinery for translation, polypeptide synthesis Figure Concept : Genes specify proteins via transcription and translation Evidence from the Study of Metabolic Defects In 1909, British physician Archibald Garrod Was the first to suggest that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell Nutritional Mutants in Neurospora: Scientific Inquiry Beadle and Tatum causes bread mold to mutate with X-rays Creating mutants that could not survive on minimal medium Using genetic crosses They determined that .
