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Unformatted text preview: C 9 (Draft) Proteins and their synthesis Students should accomplish sections 9.1 and Yanofsky’s work pp275-278 on their own. I will assume that you know this material for quizzes and tests. Translation Define translation : The use of the information in an mRNA molecule to order the amino acids in a protein. Translation is one of the most highly conserved processes and among the most energetically costly. In rapidly growing bacterial cells up to 80% of the cell’s energy and 50% of the dry weight are dedicated to protein synthesis. Synthesis of a single protein requires the coordinated action of over 100 proteins and RNAs. The Genetic Code Terminology for the three-nucleotide unit of information. The code = DNA The codon = mRNA The anticodon = tRNA loop Anticodon pairs with the mRNA codon. In each case when pairing occurs the paring is antiparallel . Three bases are one unit of information. It is usually a Nonoverlapping code. (What observations are congruent with this?) Example of overlapping code. If you mutate a completely overlapping code how many amino acids would be affected? Are alternative reading frames used to produce different proteins from the same stretch of DNA? A few examples have been found. How was the number of letters in a unit of information determined? A mathematical argument was used. 1 base and only four amino acids can be specified. One for A, one for G, etc. A two letter code produces 4 squared possibilities which could code for 16 amino acids. 4 cubed = 64 and predicts that there might be synonyms and code is degenerate . Meaning some amino acids specified by more than one triplet code. Frameshift mutation; Text pp 279-280. The sequence in English, THECATATETHERAT, read in the proper frame reads: THE CAT ATE THE RAT If we add or subtract a number of nucleotides that are not a multiple of three a frame shift mutation occurs: THE GCA TAT ETH ERA T ^ Notice that most frame shifts are very damaging to the protein. A frame shift can be somewhat corrected with another mutation(s) of equal magnitude and opposite sign: THE GCA TAT THE RAT ^ Here the correction occurs by removing the second E in the original sequence....
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