6 Translation

Question 1

How is the genetic code described?

Answer 1

degenerate, unambiguous, non overlapping and nearly universal

Question 2

what are the stop codons

Answer 2

UGA UAA UAG

Question 3

what is the start codon

Answer 3

AUG

Question 4

What is the wobble hypothesis

Answer 4

allows for the I anticodon on tRNA to bind U, C and A

Question 5

what are the different types of mutations

Answer 5

point mutations- base change leads to nonsense, missense or silent results
InDel mutations which can lead to frameshift mutations (can be from splicing)
Inversion mutations which may framshift
triplet expansion - alters proteins, may need to accumulate

Question 6

how are AA bound to tRNA?

Answer 6

via a specific aa-tRNA synthetase for each type of aa will bind the aa to CCA on 3’ of tRNA by ester bond

Question 7

how does aa-tRNA synthetase correct errors

Answer 7

the aa-tRNA synthetase have an editing site that can remove aa from tRNA if incorrect

Question 8

what does a protein chain always start with and why?

Answer 8

proteins start with methionine sine the start codon codes for it, may be changed at final product by post tran mods

Question 9

what is the general mechanism of ribosomes

Answer 9

met-tRNA binds to P site once AUG is recognized on mRNA, all other aa-tRNA binds on A site and pushes over, tRNA on E site is uncharged so leaves

Question 10

Where is the start codon usually located in

Answer 10

the kozak concensus sequence

Question 11

what does the initial tRNA have to bind to initiate?

Answer 11

it must bind to eIF4F which is eIF4A/G/E then bind to large ribosomal subunit on the P site and near the 5’ methyl cap on the mRNA

Question 12

how any eIF does proks have? euks?

Answer 12

proks 3 eIF

euks >12 eIF

Question 13

what is the start sequence for proks called?

Answer 13

shine-dalgarno sequence

Question 14

ribosome reads in which direction?

Answer 14

5’ to 3’

Question 15

what are the functions of elongation factors?

Answer 15

eEF-Tu/S (eEF-1 on euks) guides tRNA to A site
EF-G(EF-2 on euks) moves tRNA from A to P and P to E sites

Uses up GTP in the process

Question 16

how is aa added to the protein chain at the P site?

Answer 16

peptidyl transferase RIBOZYME forms a peptide bond from AA to COOH end of protein

Question 17

how does termination of RNA translation occur

Answer 17

stop codon is reached and release factors and peptidyl transferase hydrolyzes bond on last tRNA and protein

Question 18

What are polysomes and their reason

Answer 18

multiple ribosomes working on the same mRNA at different areas due to short longevity of mRNA and increased efficiency

Question 19

what is the difference in initial aa residues in proks and euks?

Answer 19

fMet for proks and Met for euks

Question 20

how is fMet created?

Answer 20

formyl transferase is used

Question 21

what does post tran mod do

Answer 21

mods function, activity and targeting of final protein

Question 22

how are proteins to be secreted synthed?

Answer 22

a signal peptide binds at SRP of newly forming protein which will direct it to rER SRP receptor and protein continues to be synthed into the pore of rER and then have signal peptide cleaved off by signal peptidase

Question 23

how are proteins targeted for degradation modified?

Answer 23

they have a mannose6p tag

Question 24

what occurs when phosphotransferases like hexoaminidase A is deficient?

Answer 24

M6P cannot bind and ends up with I(nclusion) cell diseases like tay sachs which leads to accumulating odd proteins

Question 25

give 4 examples of protein inhibitors and how they work

Answer 25

streptomycin binds 16S rRNA of 30S subunit and blocks initiation

Tetracycline binds 30S and inhibits A site binding (elongation)

Chloramphenicol binds 50S and inhibits peptidyl transferase (elongation) adverse mito

Erythromycin binds 50S prevents A to P translocation