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TRANSLATION
Building a Protein
Central Dogma of Molecular Biology
mRNA translated to polypeptide/protein
Central Dogma of Molecular Biology
mRNA translated to polypeptide/protein
nucleotide sequence
amino acid sequence
The Genetic Code
The Genetic Code- Triplet
CODON
3 bases specify 1 amino acid
- Non-overlapping
each base is only part of one codon
e.g. AUCAGUCUA AUC, AGU, CUA
not AUC, UCA, CAG, AGU, GUC, UCU, CUA
The Genetic Code- Continuous
not punctuated no additional chemical groups designate the start or end of a codon
However, it contains directions for starting or stopping translation:
AUG (Start) UAA (Stop)UAG (Stop)UGA (Stop)
The Genetic Code- Universal
All organisms use the same genetic code.
All life on earth evolved from a common ancestor.
Recombinant DNA Technology Green Fluorescent Mice!!!
The Genetic Code- Redundant…
Some amino acids were specified by more than one codon.
… But not ambiguous
No two amino acids are coded for by the same codon.
- Degenerate (WOBBLE EFFECT)Different codons coding for the same amino acid
differ only by the base in the 3rd position.
protection vs. mutation
TRANSLATION
mRNA
tRNA (carrying amino acids)
ribosomes
+ ATP
TRANSLATION
Stages:
1) INITIATION
2) ELONGATION
3) TERMINATION
TRANSLATION: Initiation
- mRNA binds to rRNA in the small ribosomal unit
- AUG (Start) attracts initiator tRNA carrying fmet
INITIATION COMPLEX
TRANSLATION: Elongation
- large ribosomal sub-unit attaches to the initiation complex
- next codon bonds to its complementary anticodon
- enzyme joins two amino acids together in a peptide bond
- first tRNA is releases as ribosome moves on to the next codon
TRANSLATION: Termination- elongation halts when “Stop” codon is reached
binding of release factor- last tRNA released- mRNA & polypeptide released & ribosomal sub-units
separate
Polyribosomes
mRNA can be translated by several ribosomes at a time.
Time for practice…
- From which labeled structure is structure D made? Identify.- Identify structure F. What does it specify?- What is structure E? What does it specify?
- What would happen to structure F if structure C were deleted?- What effect would the deletion of structure C have on the
process that occurs in step Y?