HW #17 - AP Biology Period 4#22 Liem Nguyen...

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AP Biology Period – 4 #22 Liem Nguyen 11/14/09 Homework #17 (091120): Chapter 17 (due Friday 091120) Total points: 20 for Attempt on all questions ONE Concept Map: 10 points Gene to Proteins Objectives The Connection Between Genes and Proteins 1. Explain why dwarf peas have shorter stems than tall varieties. have growth hormones gibberellins stimulate elongation of stem Dwarf peas have shorter stems than tall varieties because they lack growth hormones, called gibberellins, that stimulate stem elongation. 2. Explain the reasoning that led Archibald Garrod to first suggest that genes dictate phenotypes through enzymes. Archibald Garrod: British physician (1909) suggested genes dictated phenotypes through enzymes Alkaptonuria: hereditary condition Garrod suggested that alkaptonuria, a hereditary condition, produced black urine from the lack of alkapton enzymes. Scientists conducted research decades later, which supported the hypothesis that genes dictate the production of an enzyme. 3. Describe Beadle and Tatum’s experiments with Neurospora and explain the contribution they made to our understanding of how genes control metabolism. Beadle & Tatum worked with Neurospora experiments prove genes control metabolism Beadle and Tatum bombarded Neorospora with x-rays, then looked for mutants differing in nutritional needs from wild-type models. Mutants could not feed but can survive on a complete growth medium, so they concluded that their genes could be mutated and changed to regulate their own metabolism. 4. Distinguish between the “one gene–one enzyme” hypothesis and the “one gene–one polypeptide” hypothesis and explain why the original hypothesis was changed. Beadle and Tatums: support one-gene-one enzyme changed to “one-gene-one polypeptide” The “one-gene-one enzyme” hypothesis by Beadle and Tatum states that the function of genes are to dictate production of specific enzymes. “One-gene-one polypeptide” formed when biologists noticed proteins were not always enzymes but gene products.
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5. Explain how RNA differs from DNA. RNA (ribonucleic acid) DNA (deoxyribonucleic acid) DNA: thymine RNA: uracil DNA and RNA differ in the arrangement of nitrogenous bases. DNA is deoxyribonucleic acid and RNA is ribonucleic acid. RNA contains uracil as a nitrogenous base, in place of thymine that is present in DNA. 6. Briefly explain how information flows from gene to protein. from transcription mRNA (messenger) translation to the ribosomes Flow of information starts at transcription, the synthesis of RNA under DNA. After that, mRNA carries genetic messages to the rest of cell. Translation is where protein synthesis occurs under the directions of the messenger RNA.
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HW #17 - AP Biology Period 4#22 Liem Nguyen...

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