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Translation. Need message mRNA Need translator molecule tRNA Need site ribosome rRNA + protein. tRNA. transcribed from DNA binds to other nucleic acids binds to amino acids. Charging of tRNA. attaching amino acid to 3’ end requires specific enzyme requires energy.
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Translation • Need message • mRNA • Need translator molecule • tRNA • Need site • ribosome • rRNA + protein
tRNA • transcribed from DNA • binds to other nucleic acids • binds to amino acids
Charging of tRNA • attaching amino acid to 3’ end • requires specific enzyme • requires energy aminoacyl tRNA:
The Genetic Code • Non-overlapping • one base belongs to one codon only • every three bases “read” as one codon • No “punctuation” • no bases skipped • Special start and stop codons • AUG = start signal • UGA, UAA, UAG = stop signals
Reading Frames 5’ C C G U A U G C G G A A C U C C A U G G G A A G First amino acid in any polypeptide chain is methionine (formylmethionine – prokaryotes)
Ribosome A = aminoacyl site P = peptidyl site Small subunit P A Large subunit P = “donor” site A = “entry” site (E = “exit” site)
P A 5
5’ CAGGAAGCGAUGGGCUCGACAUGCGA… Shine-Dalgarno Sequence (prokaryotes) or Scanning Hypothesis (eukaryotes)
UAC UAC met met 5’ AUG
CCG CCG gly gly 5’ GGC AUG UAC met | met
AGC AGC ser ser AUG GGC UCG CCG gly met gly met
UGU UGU thr thr AUG GGC UCG ACA AGC ser gly met ser glu met
ACA UGA UGU Release factors thr ser glu met
ACA UGA UGU Release factors thr ser glu met
ACA UGA Release factors UGU thr ser glu met
thr ser glu met