Translation Flashcards
What is the genetic code?
Translation of nucleotide sequence to amino acid sequence,
More than one codon possible for an amino acid but not the other way around.
How many possibilities are there for an open reading frame?
3 Possibilities, but only one encodes the protein.
What is the function of trna?
Has an anticodon that pairs with complementary mRNA and 3’ end where amino acid binds.
What does amino acyl trna synthetase do?
Catalyzes the addition of the correct amino acid to the tRNA
What makes the wobble position unique in anticodon base pairing?
Wobble base can pair with multiple bases in the anticodon position
Describe ribosomes
composed of rrna and proteins, includes small subunit for codon/anticodon pairing and large subunit that catalyzed peptide bond formation .
What are the different sites of the ribosomes?
Aminoacyl-trna site, peptidyl-trna site, exit
What causes initiation of translation?
mRNA needs to have 5’-cap and poly-A tail
eIF4G/E associated with cap and tail Starts at AUG
eiF4G binds ribosome to mrna
eIF4E is a eukaryotic translation initiation factor involved in directing ribosomes to the cap structure of mRNAs.
What are the steps of translation?
- New trna binds at A site, outgoing trna leaves at E site.
- Formation of a new peptide bond by peptidyl transferase of large subunit.
- Large subunit translocates
- Small subunit translocates moving the mRNA 3 nucleotides.
Note: mRNA is read 5’ to 3’
Describe peptide bond formation
Amino acids are added to the C-terminal end of the polypeptide chain.
High energy bond between amino acid and tRNA provides energy for addition of the next amino acid.
What is involved in proofreading during translation?
Elongation factors are involved in translation. Proofreading is done by rRNA via H-bond formation.
EF-Tu – bound to GTP and incoming amino acids, helps with proofreading.
EF-G – hydrolyzes GDP, energy from hydrolysis helps movement of ribosome
Describe termination of translation.
A stop codon is reached, water is added instead of amino acid, releasing the peptide chain. mrna is released and ribosomal subunits dissociate.
Describe polyribosomes
Single RNA associated with many ribosomes.
What do chaperones do?
They bind partially folded polypeptides to help them fold, minimizing energy use for folding process and preventing inappropriate association of unfolded proteins.
Describe Hsp70 and Hsp60 proteins.
Hsp70 associated with the protein being translated and Hsp60 are large chaperone complexes.
What does the polyubiquitin chain do?
Marks proteins for degradation
What does the proteasome cap do?
Recognizes protein to be degraded and helps thread it into the core (requires ATP)
The core contains proteases that help degrade the protein.
Describe what ubiquitination requires.
E1: Ubiquitin activating enzyme, loads Ubiquitin onto E2
E2: Ubiquitin-conjugating enzymes, transfers ubiquitin onto protein, catalyzes reaction where ubiquitin is added to lysine.
E2/E3 Ubiquitin ligase, recognizes degradation signals exposed as a result of protein misfolding.
What does Polymerase chain reaction require?
Template DNA, Deoxynuceleotides, DNA polymerase, Primers
How does temperature affect PCR?
Heat separates the strands and cooling it anneals the primers and allows for elongation.
What happens in gel electrophoresis?
Fragments migrate towards positive end with the smallest fragments reaching the end first.
Whats significant about DNA sequencing?
ddnTPs are added that terminate the chain and result in smaller fragments.
Sequences determined through flourescence.
What is next generation dna sequencing?
Lots of fragments are snapshotted when nucleotides are added, info is taken on computer and helps us determine DNA sequence.
