Translation

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