Coli genes for a subunit of tyrptophan synthetase

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Unformatted text preview: of tyrptophan synthetase compared mutations within a gene to particular amino acid substitutions. Created Trp- mutants in trpA Created fine structure recombination map Determined amino acid sequences of mutants and was able to determine several results A codon is composed of more than one nucleotide. Different point mutations may affect same amino acid. Codon contains more than one nucleotide. Each nucleotide is part of only a single codon. Each point mutation altered only one amino acid. A codon is composed of three nucleotides and the starting point of each gene establishes a reading frame studies of frameshift mutations in bacteriophage T4 rIIB gene Fig. 8.5 Most amino acids are specified by more than one codon. Phenotypic effect of frameshifts depends on if reading frame is restored. Fig. 8.6 Cracking the code: biochemical manipulations revealed which codons represent which amino acids The discovery of messenger RNAs, molecules for transporting genetic information Protein synthesis takes place in cytoplasm deduced from radioactive tagging of amino acids. RNA, an intermediate molecule made in nucleus and transports DNA information to cytoplasm Synthetic mRNAs and in vitro translation determines which codons designate which amino acids 1961 Marshall Nirenberg and Heinrich Matthaei created mRNAs and translated to polypeptides in vitro Polymononucleotides Polydinucleotides Polytrinucleotides Polytetranucleotides Read amino acid sequence and deduced codons Fig. 8.7 Ambiguities resolved by Nirenberg and Philip Leder using...
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