ch17 - Chapter 17: From Gene to Protein 1 Gene -1 Enzyme...

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Chapter 17: From Gene to Protein 1 Gene -1 Enzyme Function of gene is to dictate production of specific enzyme Originally thought 1 gene 1 enzyme Now we think: 1 gene - 1 polypeptide not all proteins are enzymes (e.g. keratin) proteins may be composed of 2 or more polypeptide chains, each specified by different genes Sequence of nucleotides in DNA ultimately determines sequence of amino acids in proteins Information flows gene-> protein through 2 major processes: 1) Transcription 2) Translation Transcription: Synthesis of RNA using DNA template Complimentary sequences of mRNA Same language as nucleotides Translation: Synthesis of polypeptides using mRNA template Occurs on ribosomes 4 nucleotides -> 20 amino acids 4 nucleotides: 20 amino acids…how do we code for them? Research verified flow of information through triplet code (triplet =codon) Cracking genetic code 61/64 code for amino acids Specials: 61 triplets code 20 amino acids Creates redundancy, not ambiguity
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Redundancy: 2 or more codons can code for same amino acid Ambiguity: no! each triplet codes for only one amino acid Reading frame: Sequence of left to right is critical = reading frame Example: Genetic code universal: codons same for virtually all organisms Transcription: Details Synthesis of messenger RNA (mRNA) Catalyzed by separate 2 strands of DNA add nucleotides 5’ -> 3’ link nucleotides Prokaryotes:
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ch17 - Chapter 17: From Gene to Protein 1 Gene -1 Enzyme...

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