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Lecture Biology - Chapter 15: Genes and how they work. In this chapter, you will learn to: Differentiate among the three kinds of RNA in terms of structure and function; understand the kind of code present in the nucleotide sequence of DNA; describe the process of transcription, its machinery, and end products; describe the process of translation, its machinery, and end products;. | Genes and How They Work Chapter 15 The Nature of Genes Early ideas to explain how genes work came from studying human diseases. Archibald Garrod studied alkaptonuria, 1902 Garrod recognized that the disease is inherited via a recessive allele Garrod proposed that patients with the disease lacked a particular enzyme These ideas connected genes to enzymes. The Nature of Genes Evidence for the function of genes came from studying fungus. George Beadle and Edward Tatum, 1941 studied Neurospora crassa used X-rays to damage the DNA in cells of Neurospora looked for cells with a new (mutant) phenotype caused by the damaged DNA The Nature of Genes Beadle and Tatum looked for fungal cells lacking specific enzymes. The enzymes were required for the biochemical pathway producing the amino acid arginine. They identified mutants deficient in each enzyme of the pathway. The Nature of Genes Beadle and Tatum proposed that each enzyme of the arginine pathway was encoded by a separate gene. They proposed the one gene – one enzyme hypothesis. Today we know this as the one gene – one polypeptide hypothesis. The Nature of Genes The central dogma of molecular biology states that information flows in one direction: DNA RNA protein Transcription is the flow of information from DNA to RNA. Translation is the flow of information from RNA to protein. The Genetic Code Deciphering the genetic code required determining how 4 nucleotides (A, T, G, C) could encode more than 20 amino acids. Francis Crick and Sydney Brenner determined that the DNA is read in sets of 3 nucleotides for each amino acid. The Genetic Code codon: set of 3 nucleotides that specifies a particular amino acid reading frame: the series of nucleotides read in sets of 3 (codon) only 1 reading frame is correct for encoding the correct sequence of amino acids The Genetic Code Marshall Nirenberg identified the codons that specify each amino acid. RNA molecules of only 1 nucleotide and of . | Genes and How They Work Chapter 15 The Nature of Genes Early ideas to explain how genes work came from studying human diseases. Archibald Garrod studied alkaptonuria, 1902 Garrod recognized that the disease is inherited via a recessive allele Garrod proposed that patients with the disease lacked a particular enzyme These ideas connected genes to enzymes. The Nature of Genes Evidence for the function of genes came from studying fungus. George Beadle and Edward Tatum, 1941 studied Neurospora crassa used X-rays to damage the DNA in cells of Neurospora looked for cells with a new (mutant) phenotype caused by the damaged DNA The Nature of Genes Beadle and Tatum looked for fungal cells lacking specific enzymes. The enzymes were required for the biochemical pathway producing the amino acid arginine. They identified mutants deficient in each enzyme of the pathway. The Nature of Genes Beadle and Tatum proposed that each enzyme of the arginine pathway was encoded by a separate .
