Chapter 17 From Gene to Protein
• The information content of DNA is in the form of specific sequences of
• The DNA inherites by an organism leads to specific traits by indicating the
synthesis of proteins.
• Proteins are the links between genotype and phenotypes.
• Gene Expression, the process by which DNA directs protein synthesis, includes
two stages: transcription and translation.
• In 1909, 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
• Linking genes to enzymes required understanding that cells synthesize and
degrade molecules in a series of steps, a metabolic pathway.
• Using crosses, George and Edward identified three classes of arginine- deficient
mutants, each lacking a different enzyme necessary for synthesizing arganine.
• They developed a one gene- one enzyme hypothesis, which states that each
gene dictates production of a specific enzyme.
• 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
• RNA is the intermediate between genes and the proteins for which they code.
• Transcription is the synthesis of RNA under the direction of DNA
• Transcription produces Messenger RNA (mRNA)
• Translation is the synthesis of a polypeptide, which occurs under the direction of