Genes and proteins: Translation of RNA into proteins Flashcards
What does the link between DNA coding and resulting peptide involve?
DNA transcription by RNA Polymerase.
mRNA translation by ribosomes.
Of what do proteins consist?
Amino acid chains.
How are the amino acid chains structured in proteins?
Linked together.
Specific order.
How is the specific order of amino acid chains in proteins called?
The primary structure.
From N-terminus to C-terminus.
What can the peptide chain adopt over time?
Different structures fold around itself.
What happens when peptide chains adopt different structures?
They interact with one another –> form the final protein.
How many common amino acids are found in proteins?
20.
What are the characteristics of the 20 common amino acids in proteins?
Different: Sizes. Polarity. Hydrophobicity. Charge.
How are the amino acids referred?
Single/3 -letter codes.
How can amino acids be categorised?
By:
Polarity.
Charge.
Size.
In how many levels polypeptide chains fold and interact with other chains?
4.
Why do polypeptide chains fold and interact with each other?
To produce the final 3-dimensional shape of the mature protein.
How are the amino acids arranged in a peptide chain?
Linear.
What does the linear arrangement of amino acids in a peptide chain produce?
Structural limitations.
What are the characteristics of the secondary structure of peptide chains?
Limited flexibility. Forced shape = α helices β sheets random coils loops.
Which factors stabilise the structure of peptides?
Hydrogen bonds.
Hydrophobic interactions.
Ionic bonds.
Disulphide linkages.
How do bonds and linkages stabilise the structure of the peptide?
By connecting different parts of it.
Where are the R groups of amino acids presented?
On the outside surface of the protein.
What is a common active site in enzymes?
The ‘catalytic triad’.
How is the ‘catalytic triad’ formed in an enzyme?
3-dimensional positions:
- R groups.
- Acid nucleophile.
- Base nucleophile.
What happens in translation process of RNA?
Genetic information encoded by DNA –> transcribed into mRNA –> converted into –> amino acid sequences –> polypeptides.
What does the RNAP do in RNA translation?
Uses template DNA double-stranded helix –> produces mRNA.
What is the produced mRNA based on the coding strand?
Equivalent.
What does the amino acid sequence do in RNA translation process?
It follows the coding strand.
What does the genetic use to encode the amino acids in a peptide chain?
Triplets of DNA bases.
How is the genetic code characterised?
Almost universal.
How many combinations of A, C, G, and T exist?
> 20.
What do some amino acids have?
> 1 triplet.
How are some triplets used?
As stop signals.
Where are amino acids matched to base triplets?
In the ribosome.
By which factor are amino acids matched to base triplets?
By tRNAs.
What does the universal code link?
RNA triplets - amino acids.
DNA triplets - amino acids.
How many over-lapping reading frames does a section of double-stranded DNA have that encode a protein?
6.
How many reading frames are used at a time?
- Start-codon.
Stop codon.
What is something uncommon?
Over-lapping genes.
What is the most usual start codon?
AUG.
What are the most usual in-frame stop codons?
UAA.
UAG.
UGA.
Where does the 5’ start of the DNA coding map?
To the 5’ start of the mRNA transcript + first N-terminal amino acid of protein.
Where does the 3’ end of the DNA coding map?
To the 3’ end of mRNA transcript + last C-terminal amino acid.
Where does the 3’ end of DNA coding not map?
To the poly-A tail.
By what is the stop codon not represented?
An amino acid.
What are the tRNAs?
Short RNA molecules.
What is the structure of tRNAs?
‘t’.
‘L’.
Neck linked to specific amino acid.
Foot matches mRNA triplet.
What is the forever amino acid attachment site on tRNA?
CCA.
Where do Hydrogen bonds between paired bases in tRNA result?
3-dimensional structure.
What does Aminoacyl tRNA synthase do?
It links each amino acid to its relative tRNA.
What does the linking of amino acids to relative tRNAs need?
Energy: ATP.
How is the bond between amino acids and relatives tRNAs characterised?
Unstable.
What does the charged tRNA deliver?
The amino acid to the ribosome.
What are ribosomes?
Very large.
Multi-protein.
Multi-RNA (rRNA).
Complexes.
What are the differences between prokaryotic and eukaryotic ribosomes?
rRNAs sizes.
Main protein subunits.
What does the ribosome tighten?
mRNA between smaller 30S subunit and larger 50S.
Why does the ribosome tighten mRNA between large and small subunits?
To form the active structure.
What does the 50S subunit of ribosome contains?
Sites:
A
P
E.
What do the 3 sites of 50S subunit of ribosome bind?
Charged tRNAs.
What does 50S subunit of ribosomes do once it binds to charged tRNAs?
It removes the amino acid –> adds it to the growing peptide chain.
Where does the small ribosomal subunit bind?
To the mRNA.
At Shine-Dalgarno sequence.
–> special charged tRNA (fMet) in P site.
What does the fMet/charged tRNA in P site recognise?
The translation start codon (ATG).
By what is the charged tRNA delivered to the P site?
By EF-Tu.
What do the new charged tRNAs recognise?
Their mRNA triplets.
Where are the new charged tRNAs delivered?
To the A site.
Where is the growing peptide held?
In the P site.
Where is the growing peptide transferred?
To the new amino acid.
How is the growing peptide transferred to the new amino acid?
In a shuffle-action along mRNA transcript.
From where is the empty tRNA released?
From the E site.
Why is the empty tRNA released form the E site?
To be re-used.
Where does EF-G help?
In the translocation process.
By what is the stop signal recognised in translation process?
By the Release factor.
What does the Release factor do once it recognises the stop signal?
It binds to the A site –> releases peptide from P site.
What happens to the ribosome after the new peptide is released?
It fall in small and large subunits.
Groups together at a new Shine-Dalgarno site on a new mRNA.
How is the translation process characterised?
Central.
Complex.
Costly.
Heavily regulated at levels.
How can sites on mRNA be hidden/uncovered?
By folding.
By RNA-binding proteins.
Why are the sites of mRNA hidden/uncovered?
To prevent/initiate translation.
Why can ribosomal subunits/other factors be targeted?
To control elongation/termination.
What are the translation control points?
Antibiotic/antibiotic resistance targets.
