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;. | From Gene to Protein Chapter 17 Overview: The Flow of Genetic Information The information content of DNA is in the form of specific sequences of nucleotides The DNA inherited by an organism leads to specific traits by dictating the synthesis of proteins Proteins are the links between genotype and phenotype Gene expression, the process by which DNA directs protein synthesis, includes two stages: transcription and translation © 2011 Pearson Education, Inc. Concept : Genes specify proteins via transcription and translation How was the fundamental relationship between genes and proteins discovered? © 2011 Pearson Education, Inc. Evidence from the Study of Metabolic Defects In 1902, British physician Archibald Garrod first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions He thought symptoms of an inherited disease reflect an inability to synthesize a certain enzyme Linking genes to enzymes required understanding that | From Gene to Protein Chapter 17 Overview: The Flow of Genetic Information The information content of DNA is in the form of specific sequences of nucleotides The DNA inherited by an organism leads to specific traits by dictating the synthesis of proteins Proteins are the links between genotype and phenotype Gene expression, the process by which DNA directs protein synthesis, includes two stages: transcription and translation © 2011 Pearson Education, Inc. Concept : Genes specify proteins via transcription and translation How was the fundamental relationship between genes and proteins discovered? © 2011 Pearson Education, Inc. Evidence from the Study of Metabolic Defects In 1902, British physician Archibald Garrod first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions He thought symptoms of an inherited disease reflect an inability to synthesize a certain enzyme Linking genes to enzymes required understanding that cells synthesize and degrade molecules in a series of steps, a metabolic pathway © 2011 Pearson Education, Inc. Nutritional Mutants in Neurospora: Scientific Inquiry George Beadle and Edward Tatum exposed bread mold to X-rays, creating mutants that were unable to survive on minimal media Using crosses, they and their coworkers identified three classes of arginine-deficient mutants, each lacking a different enzyme necessary for synthesizing arginine They developed a one gene–one enzyme hypothesis, which states that each gene dictates production of a specific enzyme © 2011 Pearson Education, Inc. The Products of Gene Expression: A Developing Story Some proteins aren’t enzymes, so researchers later revised the hypothesis: one gene–one protein Many proteins are composed of several polypeptides, each of which has its own gene Therefore, Beadle and Tatum’s hypothesis is now restated as the one gene–one polypeptide hypothesis Note that it is common to refer to gene products as
