51to53Centraldogmatranscription - Chapter 5: Protein...

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Unformatted text preview: Chapter 5: Protein Synthesis 5.1. One Gene-One Polypeptide Hypothesis (pp. 234-236) Describe the relationship bet. genes and proteins. How might an error in a gene result in a change in protein sequence? (Q1, p. 236.) Gene: sequence of nucleotides (usually DNA) coding for the prod. of a specific protein Protein: folded polypeptide (chain of amino acids) performing a biol. function Gene codes for the correct sequencing of amino acids in making a polypeptide protein. - if error in the gene error in the sequencing of amino acids in making a polypeptide prod. of defective protein or different protein Describe Garrods observational evidence that helped him form his hypothesis. Explain what he meant by the phrase inborn error of metabolism. (Q2, p. 236) Garrod (1909) : hypothesized that one gene one protein (enzyme) * first to hypothesize that genes involved in making metabolic proteins - alkaptonuria (inherited disorder): high [alkapton] deep red/black urine people with alkaptonuria have a defective enzyme that breaks down alkapton - e.g. A B C; if [A] is high, then enzyme A is defective enzyme A enzyme B (i.e. enzyme A is not breaking down A) Inborn Error of Metabolism: - this deficient enzyme observed to run in families (i.e. alkaptonuria is hereditary) * enzyme must be controlled by a single gene In Beadle and Tatums experiment using the organism Neurospora crassa , why was it important to use organisms that were mutated in one gene? Explain why it was important to grow the mutant strains on minimal media containing only one additional nutrient. (Q4, p. 236.) Beadle and Tatum (1941): confirmed that one gene one protein - if indeed one gene one specific enzyme; - then it should be possible to create mutant organisms with defective genes, these mutant organisms cant complete certain enzyme-driven biochem. rxns (such as the arginine biochem. pathway) - fungi: Neurospora crassa (red bread mold) - when bare-minimal nutrients were available, healthy Neurospora sp. can grow because it prod. all of its own amino acids + vitamins necessary for growth mutant Neurospora sp. cant grow because it wont prod 1+ compounds necessary (exposed to radiation) for growth - mutant Neurospora sp. grew in bare-minimal nutrients + 1 additional nutrient precursor ornithine citruilline argininosuccinate arginine enzyme A...
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51to53Centraldogmatranscription - Chapter 5: Protein...

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