Biology Chapter 17 Objectives

Biology Chapter 17 - Chapter 17 From Gene to Protein The Connection Between Genes and Proteins 1 Dwarf peas have shorter stems than tall varieties

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Chapter 17 From Gene to Protein The Connection Between Genes and Proteins 1. Dwarf peas have shorter stems than tall varieties because they lack growth hormones called gibberellins, which stimulate the normal elongation of stems. 2. Archibald Garrod first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cells. He postulated that the symptoms of an inherited disease reflected a person’s inability to make a particular enzyme. 3. Beadle and Tatum began working with bread mold, Neurospora crassa. They bombarded Neurospora with X-rays and then looked among the survivors for mutants that differed in their nutritional needs from the wild-type mold. Beadle and Tatum identified mutants that could not survive on minimal medium, apparently because they were unable to synthesize certain essential molecules from the minimal ingredients. They took samples from the mutant growing on complete medium and distributed them to a number of different vials that contained minimal medium plus a single additional nutrient. The particular supplement that allowed growth indicated the metabolic defect. Each mutant was defective gene. As a result, Beadle and Tatum’s results provided strong support for the one gene – one enzyme hypothesis which states that the function of a gene is to dictate the production of a specific enzyme. Their contributions showed how a combination of genetics and biochemistry could be used to work out the steps in a metabolic pathway. 4. The original one gene – one enzyme hypothesis states that the function of a gene is to dictate the production of a specific enzyme. The one gene – one polypeptide hypothesis states that a gene is a segment of DNA that codes for one polypeptide. The original hypothesis was changed because not all proteins are enzymes. 5. RNA differs from RNA because it contains ribose instead of deoxyribose as its sugar, and has the nitrogenous base uracil rather than thymine. Thus, each nucleotide along a DNA strand has A, G, C, or T as its base, and each nucleotide along an RNA strand has A, G, C, or U as its base. An RNA molecule also usually consists of a single strand. 6. Information flows from gene to protein through two major stages, transcription and translation. Transcription is the synthesis of RNA under the direction of DNA. Translation is the actual synthesis of a polypeptide which occurs under the direction of RNA molecule messenger RNA, or mRNA. The cell translates the base sequence of an mRNA molecule into the amino acid sequence of a polypeptide. 7.
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This note was uploaded on 08/29/2009 for the course BIOL 101 taught by Professor Sakji during the Fall '08 term at Linn Tech.

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Biology Chapter 17 - Chapter 17 From Gene to Protein The Connection Between Genes and Proteins 1 Dwarf peas have shorter stems than tall varieties

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