11-Translation

11-Translation - The Genetic Code & Translation the...

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the genetic code mutations ribosomes transfer RNA initiation of translation elongation termination of translation translation-disrupting antibiotics amino acids and polypeptides The evolution of the gene concept biosynthetic pathways hemoglobin and quaternary structures
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The genetic code Codon : a three-base sequence of DNA that codes for an amino acid. expressed in the table as mRNA start codon: AUG stop codons: UAA, UAG, and UGA (do not code for amino acids)
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The genetic code
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Characteristics of the genetic code Unambiguous : each of the 61 triplets code for only one of the 20 amino acids Degenerate : most amino acids are be encoded by more than one codon Universal : most species studied use the same code, but exceptions exist Commaless : there are no breaks between the codons (all the bases of the translated sequences are part of codons) Non-overlapping : codon triplets are in tandem sequence and do not overlap
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The flow of genetic information DNA mRNA Protein
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The insertion of a single base results in a frameshift mutation All the codons from the insertion site on are changed.
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Substitution mutations A base is replaced by a different base resulting in a single codon change . Silent : the resulting new codon codes for the same amino acid as the original codon Missense : the new codon codes for a different amino acid Nonsense : the new codon is a stop codon (resulting in a shorter polypeptide)
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Wild-type AUG ACA CGG AGU AGA UAU UAA Met Thr Arg Ser Arg Tyr Stop Silent AUG ACA CGG AG C AGA UAU UAA Met Thr Arg Ser Arg Tyr Stop Missense AUG ACA CGG A A U AGA UAU UAA change G in Met Thr Arg Asn Arg Tyr Stop Ser codon to A Nonsense AUG ACA CGG AGU U GA UAU UAA change A in Met Thr Arg Ser Stop the 2nd Arg codon to U Substitution mutations
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Overlapping genes The same locus codes for two different gene products . the choice of initiation codon determines the reading frame and the resulting sequence of amino acids in the polypeptide Reading frame : a linear sequence of codons in a nucleic acid defined by a start codon
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Basic requirements : mRNA ribosome charged transfer RNAs (tRNAs) other requirements : initiation factors, elongation factors, and energy sources Translation
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11-Translation - The Genetic Code & Translation the...

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