BIO SCI 99 Problem Set

BIO SCI 99 Problem Set - The mixture was then filtered...

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1BIO SCI 99 Problem Set #3 Zoran Rakonjac Monday 11am Section 1. What experiments or observations eliminated the possibility that the genetic code was a three-letter overlapping code? What experiment or observation eliminated the possibility that there are spacers or punctuation between three-letter code words? Brenner and Crick experiment eliminated the possibility that genetic code was a three-letter overlapping code because they held the fundamentals that genetic code should be as simple as possible, also known as “Occam’s Razor.” Yanofsky experiment eliminated the possibility that there were spacers or punctuation between the three-letter code. 2. A filter binding assay was used to elucidate the genetic code. In one such assay 14 C-labeled phenylalanine- tRNA and the nineteen other unlabeled charged tRNAs were incubated with the tri-nucleotide pUpUpU and ribosomes.
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Unformatted text preview: The mixture was then filtered through nitrocellulose. What was retained on the filter? Only ribosome/tRNA/mRNA complexes where tRNA* (Trp) and mRNA (UGG) were complementary retain on the filter. 3. Which tRNA anti-codons will not be found in normal cells? There is no tRNA for the stop codons at the end of the gene (Open Reading Frame). 4. How many different RNA sequences could code for the peptide ALA ASN THR GLU ALA THR GLU ARG SER (ANTEATERS)? 49 different RNA sequences would code for the peptide ANTEATER because each amino acid has more than one codon sequence coding for its respective amino acid (they range in numbers). 5. Why is it that N-formylmethionine cannot be used to elongate a polypeptide chain? N-formylmethionine is used for initiation of polypetide chain formation. For elongation, aminoacyl-tRNA is used along with elongation factors and GTP....
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