Lecture 9 - Protein Synthesis

Question 1

what is pre mRNA capping?

Answer 1

needs an s’ cap - composed of phosphorylated 7-methyl guanosine which is added to the s’ end by gunnel transferase to ensure mRNA is transported out of the nucleus and blocks degradation of mRNA by 5’ exonuclease

Question 2

what is polyadenylation of pre mRNA

Answer 2

needs a 3’ poly-A- tail as pre mRNA is cleaved by an endonuclease near AAUAAA sequence at the 3’ end, approximately 200 adenosine residues are added to the cleavage site by poly-a-polymerase and protects the mRNA from degradation by 3’exonucleases and aids in termination of transcription

Question 3

what does alternative splicing produce?

Answer 3

produces different proteins from the same gene

Question 4

what is the order of mature mRNA ?

Answer 4

s’cap, s’UTR, coding region, 3’UTR, poly(A)tail

Question 5

what is UTR?

Answer 5

untranslated region

Question 6

what are the different ribosome types?

Answer 6

40s, 60s and 80s

Question 7

what are the 3 types of tRNA?

Answer 7

aminoacyl - one amino acid attached
peptidyl - multiple amino acids attached
deacylated - amino acid removed

Question 8

what is initiation?

Answer 8

binding of ribosomes to 5’ end of mRNA and H+ binding at the anticodon on an aminoacylated tRNA carrying methionine on the AUG start codon

Question 9

what is elongation?

Answer 9

addition of further amino acids to the growing polypeptide chain brought by corresponding aminoacylated tRNAs. peptdyl transferase creates covalent peptide bonds between amino acids

Question 10

what is termination?

Answer 10

when stop codons are reached and peptide and ribosomal subunits are released

Question 11

In what direction does translation occur ?

Answer 11

move from 5’ to 3’ end