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20.5: Key Terms

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    139569
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    minoacyl tRNA synthetase
    enzyme that “charges” tRNA molecules by catalyzing a bond between the tRNA and a corresponding amino acid
    anticodon
    three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon
    central dogma
    states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins
    codon
    three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation
    colinear
    in terms of RNA and protein, three “units” of RNA (nucleotides) specify one “unit” of protein (amino acid) in a consecutive fashion
    degeneracy
    (of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous
    hairpin
    structure of RNA when it folds back on itself and forms intramolecular hydrogen bonds between complementary nucleotides
    initiator tRNA
    in prokaryotes, called tRNAfMettRNAfMet; in eukaryotes, called tRNAi; a tRNA that interacts with a start codon, binds directly to the ribosome P site, and links to a special methionine to begin a polypeptide chain
    Kozak’s rules
    determines the correct initiation AUG in a eukaryotic mRNA; the following consensus sequence must appear around the AUG: 5’-GCC(purine)CCAUGG-3’; the bolded bases are most important
    nonsense codon
    one of the three mRNA codons that specifies termination of translation
    peptidyl transferase
    RNA-based enzyme that is integrated into the 50S ribosomal subunit and catalyzes the formation of peptide bonds
    polysome
    mRNA molecule simultaneously being translated by many ribosomes all going in the same direction
    reading frame
    sequence of triplet codons in mRNA that specify a particular protein; a ribosome shift of one or two nucleotides in either direction completely abolishes synthesis of that protein
    rho-dependent termination
    in prokaryotes, termination of transcription by an interaction between RNA polymerase and the rho protein at a run of G nucleotides on the DNA template
    Shine-Dalgarno sequence
    (AGGAGG); initiates prokaryotic translation by interacting with rRNA molecules comprising the 30S ribosome
    signal sequence
    short tail of amino acids that directs a protein to a specific cellular compartment
    start codon
    AUG (or rarely, GUG) on an mRNA from which translation begins; always specifies methionine
    template strand
    strand of DNA that specifies the complementary mRNA molecule
    transcription bubble
    region of locally unwound DNA that allows for transcription of mRNA

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