translation - ms. kropactranslation sunday, november 19, 17 happens after transcription mrna →...
TRANSCRIPT
Translation
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Happens after transcriptionmRNA → proteinAlso has an initiation, elongation, and termination phase
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Codons
Uses codons - sequences of DNA or RNA nucleotides that correspond with a specific amino acid
Example: ATT codes for the amino acid isoleucine
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tRNA
tRNA (transfer RNA) are free floating, single stranded amino acids
have a cloverleaf shape
acceptor stem
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tRNA
have a unique anti-codon, inversely reacts to each codon on mRNA
acceptor stem
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tRNA
acceptor stem: contains the amino acid that corresponds with the codon on mRNA
acceptor stem
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tRNA
aminoacyl-tRNA synthetase: enzyme that places the correct amino acid to the proper tRNA molecule
acceptor stem
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tRNA
each tRNA carries only one anticodon and one amino acid
acceptor stem
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Initiation
The building of proteins, happens at the ribosome
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Initiation
Starts with the ‘start codon’ AUG, codes for methionine
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InitiationInitiation factors assemble the:
small ribosomal sub-unit
mRNA
initiator tRNA
large ribosomal sub-unit
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Initiation
Ribosomes have three sites that tRNA binds to
the acceptor (A) site
the peptide (P) site
the exit (E) site
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Initiation
the P site contains the tRNA molecule attached to the growing polypeptide chain
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Initiation
the A site contains the tRNA that is carrying the next amino acid to be added to the polypeptide chain growing in the P site
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Initiation
the E site is where the uncharged tRNA (no amino acid attached) is ejected from the ribosome
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Initiation
the initiator tRNA binds to the P site
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Elongation
Initiator tRNA is at the P site
the next codon on the mRNA is at the A site
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Elongation
the tRNA with the complementary anticodon will also occupy the A site (bonding through base pairs on the tRNA and mRNA)
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Elongationthe amino acid on the other end of the tRNA will be bonded amino acid attached to tRNA codon using a peptide bond.
The resulting peptide is now attached to the tRNA molecule present at the A site
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Elongation
the mRNA will move along by one codon shifting the dipeptide from the A site to the P site
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Elongation
the tRNA that carried the free amino acid is now uncharged and located at the E site. It will exit from the ribosome and go bind to another amino acid.
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Elongation
the A site is now open and ready to accept the next tRNA that is complementary to the codon on the mRNA
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Terminationthe polypeptide is released when a stop codon enters the A site.
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Terminationa release factor cleaves the polypeptide from the last tRNA
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