1 PROTEIN SYNTHESIS: Translation. 2 Transcription Translation DNA mRNA Ribosome Protein Prokaryotic...
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Transcript of 1 PROTEIN SYNTHESIS: Translation. 2 Transcription Translation DNA mRNA Ribosome Protein Prokaryotic...
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PROTEIN PROTEIN SYNTHESIS: SYNTHESIS: TranslationTranslation
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TranscriptionTranscription
TranslationTranslation
DNA
mRNA
Ribosome
Protein
Prokaryotic CellProkaryotic Cell
DNA DNA RNA RNA ProteinProtein
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The Genetic Code
1. is redundant- more than one codon can code for the same
amino acid
2. is continuous- reads as a series of 3-letter codons without
spaces
3. is nearly universal- almost all organisms build proteins with the same
code
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gene expression
• the transfer of genetic information from DNA to RNA to protein
TranslationTranslationmRNA is exported to the cytoplasm and
processed further by other enzymes to remove the “junk” DNA called introns
The final mRNA is transported to ribosomes where translation occurs.
Ribosomes read the mRNA in multiples of 3 nucleotides called codons
For example:5’ AUGCCCUCAGAG 3’
Codon TableCodon Table
TranslationTranslationEach codon signals the cell to retrieve
and add an amino acid to a growing chain of amino acids using transfer RNA (tRNA).
energy is used to both make the amino acids and to join them, ~200 ATP per 50 aa sequence!
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tRNA
• transfer RNA
• ssRNA, ~80 nucleotides, that has an anticodon loop and a 3’ region where an amino acid attaches
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Steps of Translation
1. Initiation• small ribosomal subunit attaches at 5’cap
and scans down
• the anticodon of tRNA attaches to the AUG start codon of mRNA, using the small ribosomal subunit as “support”
– this sets the reading frame
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• large ribosomal subunit joins – P (peptide) site: where first tRNA binds– A (amino acid) site: where next tRNA will bind– E (exit) site: where tRNA will leave from
• the ribosome is made or rRNA and proteins• made inside the cell’s nucleus
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2. Elongation
- the large ribosomal subunit catalyzes the peptide bond between the P site and the A site amino acids
- mRNA moves forward by one codon
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3. Termination
• stop codon is reached, ribosome falls off
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TranscriptioTranscriptionn
TranslatiTranslationon
AA sequence = Protein!AA sequence = Protein!Once the entire mRNA
sequence is read and translated into amino acids the chain of AA’s is released
This chain of AA’s folds and contorts into a structure called its tertiary structure*
Finally a functional protein!
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• The end….ignore the rest
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RibosomesRibosomes
PSite
ASite
Largesubunit
Small subunit
mRNAmRNA
A U G C U A C U U C G
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mRNA Codons Join the mRNA Codons Join the RibosomeRibosome
PSite
ASite
Largesubunit
Small subunit
mRNAmRNA
A U G C U A C U U C G
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InitiationInitiation
mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa2
A U
A
1-tRNA
U A C
aa1
anticodon
hydrogenbonds codon
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mRNAmRNA
A U G C U A C U U C G
1-tRNA 2-tRNA
U A C G
aa1 aa2
A UA
anticodon
hydrogenbonds codon
peptide bond
3-tRNA
G A A
aa3
ElongationElongation
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mRNAmRNA
A U G C U A C U U C G
1-tRNA
2-tRNA
U A C
G
aa1
aa2
A UA
peptide bond
3-tRNA
G A A
aa3
Ribosomes move over one codon
(leaves)
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mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa1
aa2
A UA
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
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mRNAmRNA
A U G C U A C U U C G
2-tRNA
G
aa1aa2
A U
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
(leaves)
Ribosomes move over one codon
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mRNAmRNA
G C U A C U U C G
aa1aa2
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
U G A
5-tRNA
aa5
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mRNAmRNA
G C U A C U U C G
aa1aa2
A
peptide bonds
3-tRNA
G A A
aa3
4-tRNA
G C U
aa4
A C U
U G A
5-tRNA
aa5
Ribosomes move over one codon
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mRNAmRNA
A C A U G U
aa1
aa2
U
primaryprimarystructurestructureof a proteinof a protein
aa3
200-tRNA
aa4
U A G
aa5
C U
aa200
aa199
terminatorterminator or stopor stop codoncodon
TerminationTermination
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End Product –The End Product –The Protein!Protein!• The end products of protein The end products of protein
synthesis is a synthesis is a primary structureprimary structure of a proteinof a protein
• A A sequence of amino acidsequence of amino acid bonded together by peptide bonded together by peptide bondsbonds
aa1
aa2 aa3 aa4aa5
aa200
aa199
More about different types of DNA you should know about:
•Centromeric DNA (CEN) Center of chromosome, specialized sequences function with the microtubles and spindle apparatus during mitosis/meiosis.
•Telomeric DNA At extreme ends of the chromosome, maintain stability, and consist of tandem repeats. Play a role in DNA replication and stability of DNA.
•Unique-sequence DNA Often referred to as single-copy and usually code for genes.
•Repetitive-sequence DNA May be interspersed or clustered and vary in size.
SINEs short interspersed repeated sequences (100-500 bp)
LINEs long interspersed repeated sequences (>5,000 bp)
Microsatellites short tandem repeats (e.g., TTA|TTA|TTA)