Chapter 13 - Translation of mRNA Flashcards
What is translation?
mRNA codons into amino acids to make proteins
Important cellular components
Proteins, RNAs, and small molecules
What are the active participants in cell structure and function?
Proteins
Genes that encode polypeptides
Protein-encoding or structural genes
Disease characterized by black urine and blue/black discoloration of tissues
Alkaptonuria
First person to propose relationship between genes and protein production
Archibald Garrod
First person to propose relationship between genes and protein production
Archibald Garrod
Who proposed one gene - one enzyme versus one gene - many enzymes
Beadle and Tatum
A single gene controls the synthesis of a single enzyme
One gene - one enzyme hypothesis
Term that denotes structure
Polypeptide
Term that denotes function
Protein
Genes that do not encode polypeptides
Functional RNA molecules
Translation relies on…
The genetic code
Three nucleotide group of mRNA
Codon
Start Codon
AUG
Stop codons
UAA, UAG, and UGA
When more than one codon can specify the same amino acid
Degenerate code
Direction of polypeptide synthesis
5’ to 3’ parallel to mRNA
Where do peptide bonds form during elongation
Between carboxyl and amino groups
Four levels of structure in proteins
Primary, secondary, tertiary, and quaternary
Primary structure
Amino acid sequence
Secondary structure
folding into alpha helix and beta sheet
Tertiary structure
3D folding of a short region
Quaternary structure
When multiple polypeptides form a functional protein
Proteins that accelerate chemical reactions within a cell
Enzymes
Nirenberg experiments
Factors required for translation
Khorana experiments
RNA synthesis
Francis Crick experiments
Adaptor hypothesis
tRNA plays a direct role in the recognition of codons in mRNA - identifies the codon and delivers the proper amino acid
Adaptor hypothesis
Structure found in all tRNAs
3’ ACC acceptor stem
Enzymes that attach amino acids to tRNAs - result in charged tRNA
Aminoacyl-tRNA synthetases
Error rate of amino acids from tRNA
Less than 1 in 10,000
The codon-anticodon recognition process remains strict for the first two bases - the third can tolerate certain mismatches
Wobble hypothesis
Where does translation occur
Surface of the ribosome
Where are ribosomes in bacteria
Cytoplasm
Where are ribosomes in eukaryotes
One type in the cytoplasm, one type in the organelles
Ribosomes are formed of subunits containing…
Proteins and rRNA
Sedimentation coefficients in bacteria
30S, 50S, 70S
Sedimentation coefficients in eukaryotes
40S, 60S, 80S
Ribosome sites
P site, A site, E site
P Site
Peptidyl site
A Site
Aminoacyl site
E Site
Exit site
Three stages of translation
Initiation, elongation, termination
How does mRNA bind to the 30S subunit
Shine-Dalgarno sequence and hydrogen bonds
Bacterial initiation complex
mRNA, initiator tRNA, and ribosomal subunits
Eukaryotic initiation complex
mRNA, initiator tRNA, ribosomal subunits, additional initiation factors
Eukaryotic translation initiation process
initiation factor binds to 5’ mRNA, joined by 40S subunit, tRNA(met) and assembly moves along mRNA looking for start codon
After peptide bond formation
tRNAs at P and A sites move to E and P sites
What recognizes stop codon
Release factor
In bacteria, can translation occur before transcription is finished?
Yes
In eukaryotes, can translation occur before transcription is finished?
No
Coupling
Translation begins before transcription ends
How do antibiotics work?
Translation process differences between prokaryotes and eukaryotes allow translation in one to be inhibited without affecting the other
