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Lecture 11 & 12
Translation
The process of converting RNA into a protein
Gene Expression
The process where genetic information flows from DNA to RNA to protein.
Amino Acid
The building block of proteins.
Peptide Bond
a covalent bond between the carboxyl group on
one amino acid and the amino group of the next amino acid
Polypeptide
A chain of amino acids linked by peptide bonds
3D Structure
A protein's ____ determines its function.
Codon
A sequence of three nucleotides in mRNA that encodes an amino acid.
Anticodon
A sequence of three nucleotides in tRNA complementary to an mRNA codon.
Triplet Code
Each amino acid is coded by a set of three nucleotides (codon).
Non-overlapping Code
Codons are read one at a time without overlap.
No Punctuation
The genetic code is read continuously from 5’ to 3’.
Start Codon
AUG (Methionine) signals the beginning of translation.
Stop Codon
UAA, UAG, UGA signal the termination of translation.
Degeneracy
Multiple codons can code for the same amino acid.
Universal Genetic Code
The genetic code is conserved across organisms.
Crick & Brenner Experiment
Demonstrated that the genetic code is a triplet.
Nirenberg & Khorana Experiment
Deciphered which codons correspond to specific amino acids.
Pauling’s Sickle Cell Discovery
Showed that a single amino acid change alters protein function.
mRNA (messenger RNA)
carries the genetic code from DNA to ribosomes
tRNA (transfer RNA)
brings amino acids to ribosomes during translation
rRNA (ribosomal RNA)
forms part of the ribosome and catalyzes peptide bond formation
Ribosome
The molecular machine that synthesizes proteins.
Small Ribosomal Subunit
Binds to mRNA and helps initiate translation.
Large Ribosomal Subunit
Contains the enzymatic activity for peptide bond formation
A Site (Aminoacyl Site)
Binds incoming charged tRNA during elongation
P Site (Peptidyl Site)
Holds the growing polypeptide chain.
E Site (Exit Site)
Where uncharged tRNA exits the ribosome.
Aminoacyl-tRNA Synthetase
Enzyme that attaches the correct amino acid to tRNA.
Translation Initiation
The ribosome assembles on the mRNA and finds the start codon.
Shine-Dalgarno Sequence
The ribosome binding site in prokaryotic mRNA.
5' Cap Binding
The ribosome binds to the 5' cap of eukaryotic mRNA.
Translation Elongation
Successive amino acids are added to the growing chain.
Peptidyl Transferase
The enzymatic activity of the ribosome that forms peptide bonds.
Translocation
The ribosome moves one codon down the mRNA.
Translation Termination
The ribosome reaches a stop codon, and the protein is released.
Release Factors (RFs)
Proteins that recognize stop codons and terminate translation.
Ribosome Recycling
The ribosome components dissociate and can be reused.
Prokaryotic Translation
Transcription and translation are coupled.
Eukaryotic Translation
Transcription occurs in the nucleus, translation in the cytoplasm.
Polysomes
Multiple ribosomes translating a single mRNA simultaneously.
Wobble Hypothesis
Flexibility in the third base of a codon allows one tRNA to recognize multiple codons
Frameshift Mutation
Insertion or deletion of nucleotides that shifts the reading frame
Ribozyme
RNA molecules that act as enzymes (e.g., rRNA in the ribosome).
GTP hydrolysis
provides energy for translation steps.
amino terminus
start of polypeptide or protein
carboxyl terminus
end of polypeptide or protein
64
number of codons enough to identify 20 amino acids
proflavin
chemical that caused T4 mutants to no
longer infect E. coli
lysate (E. coli)
this + RNA was able to synthesize proteins
ribosome
translates the information in the sequence of codons in the mRNA into the amino sequence of the protein
mRNA
RNAs that are translated into proteins
tRNA & rRNA
RNAs that function to make other proteins
miRNA (microRNA)
siRNA (small interfering RNA)
RNAs that regulate gene expression
