HC4 translation of mRNA into protein

Question 1

DNA and RNA can be potentially translated into how many reading frames?

Answer 1

DNA: 6
RNA: 3

Question 2

Translation of mRNA in eukaryotes

Answer 2

• mRNA exported out of nucleus
• assembly of ribosomes on mRNA
• first 40S rRNA + initiation complex bind
• 60S rRNA associates –> now it is fully active
• tRNAs carry aa to the ribosome for incorporation into the polypeptide chain
• mRNA seq matches the tRNA anticodon.
• aa coupled to tRNA by aminoacyl-tRNA-synthetases

Question 3

polysomes

Answer 3

multiple ribosomes can be present on one mRNA transcript

Question 4

wobble base pairing

Answer 4

G-U pairing. thrid nucleotide of codon does not have to match the first anticodon.

Question 5

ribosome: sites + termination of translation

Answer 5

A, P and E sites. First in A (aminoacyl), then moves to P (peptidyl) and lastly E (exit).

release factor binds to A-site . this has peptidyl-transferase activity. termination by hydrolysis –> chain released from tRNA and ribosome.

Question 6

elongation of peptide chain: type of bound formed

Answer 6

peptide bond between N-terminus (NH2) of aa bound to tRNA and the C-terminus (COO) of nascent chain

Question 7

Translation initiation eukaryotes

Answer 7

pre-initiation complex and cap binding complex bind to 5’mRNA and scan mRNA for startcodon is found in the context of a kozak consensus sequence.

Question 8

translation intiation prokaryotes

Answer 8

internal initiation of translation: multiple startcodons are present in one mRNA transcript,. small subunit of rRNA binds to mRNA, scans for startcodon and then large subunit assemles + initiaitor tRNA.

Question 9

co-translational translocation

Answer 9

mRNA translation occurs at the same time while the ribosome is bound to the ER and thus is translocation into the ER. in the ER proteins get glycosylated.

Question 10

correct folding

Answer 10

chaperone proteins. Hsp70.

Question 11

incorrect folding

Answer 11

corrected by Hsp60.
can get marked for degradation by poly-ubiquitination and will be degraded by ubiquitin-proteasome system. F-box proteins recognise degradation signals in proteins target them to the E2 and E3 complex

Question 12

proofreading of translation

Answer 12

EF-Tu: catalyses binding of aminoacyl-tRNAs to the ribosome. if tRNA is incorrect, it can be removed: GTP is hydrolysed
EF-G coordinates translocation of tRNA from A-site to P-site, and then to the E-site.