translation

Question 1

what replaces the cap binding complex when the mRNA goes outside of the nucleus?

Answer 1

initiation factors for protein synthesis, elF4G, elF4E

Question 2

mRNA sequences are decoded in sets of __ nucleotides and has __ different reading frames

Answer 2

3, 3

Question 3

what is the start codon?

Answer 3

AUG, methionine, cleaved off later

Question 4

what are the 3 stop codons?

Answer 4

UAA, UAG, UGA

Question 5

what are tRNA molecules?

Answer 5

matche amino acids to triplet codons in mRNA

Question 6

what are the 2 crucial regions of tRNA?

Answer 6

anticodon- where amino acids go into, ball is 3’, other side is 5’,
3’ where amino acid is attached to-

Question 7

what is the wobble position?

Answer 7

only need accurate base pairing for the first 2 positions, some proteins have the same first 2 AA so 3rd could t anything, tRNA can base-pair with more than one codon

Question 8

who synthesizes tRNA?

Answer 8

RNA polymerase III, large precursor tRNA then spliced (not lariat, cut-paste)

Question 9

what is the enzyme that is gonna put the AA to tRNA?

Answer 9

aminoacyl-tRNA-synthase, 20 different types for each AA

Question 10

what is CCA addition?

Answer 10

at the 3’ end of all mature tRNA molecules to function as the site of amino acid attachment

Question 11

how does tRNA synthetase do quality control?

Answer 11

it can recognize correct tRNAS
correct AA has the highest affinity
editing site: correct AA will proceed while incorrect ones will be cut off

Question 12

AA is put onto a growing chain by

Answer 12

peptidyl linkage

Question 13

which subunit will catalyze peptide bond formation?

Answer 13

large subunit

Question 14

which subunit is the framework for t-RNA-mRNA codon matching?

Answer 14

small subunit

Question 15

what are the 3 sites of tRNA?

Answer 15

e, p, a site

Question 16

what is the a site?

Answer 16

accepts new tRNA that’s been charged with AA

Question 17

what is the p site?

Answer 17

…peptide

Question 18

what is the e site?

Answer 18

exit site

Question 19

how does tRNA work with ribosomes??

Answer 19

1. new tRNA comes into A site
2. peptide bond formation
3. large subunit shifts
4. small subunit shifts, tRNA at e site leaves

Question 20

what is met-tRNAi?

Answer 20

special tRNA that brings methionine to the p site of the small subunit

Question 21

what if IF?

Answer 21

initiation factors

Question 22

what is eIF?

Answer 22

eukaryotic initiation factors

Question 23

what is eEF?

Answer 23

eukaryotic elongation factor

Question 24

what is eRF?

Answer 24

eukaryotic release factor

Question 25

what is eIF2?

Answer 25

binds to small subunit at p site

Question 26

describe initiation of translation?

Answer 26

met-tRNAi is placed on p site, eIF2 is attached, other initiation factors bind to the subunit, moves to search for the first AUG, factors leave, large ribosomal subunit binds

Question 27

what is polycistronic?

Answer 27

codes for multiple proteins on the same RNA

Question 28

what are shine-dalgarno sequence

Answer 28

internal ribosome binding sites

Question 29

what is EF2 used for?

Answer 29

check to see if codon and anticodon match is correct

Question 30

describe how elongation factors work in translation?

Answer 30

EF2 binds to aminoacyl-tRNA and GETP, EF2 checks for matches, EF2 undergoes a conformation change and GTP hydrolysis occurs if correct pair. there is a time delay before AA moves into ribosome, if correct, AA has a short time delay. if incorrect, there is a delay. EF1 helps with shift of ribosome position

Question 31

what is a RF?

Answer 31

release factor, a protein , everybody dissociates

Question 32

what are polyribosomes?

Answer 32

multiple ribosomes on a mRNA

Question 33

how do antibiotics work?

Answer 33

bind to bacterial ribosomes and stopping their translational mechanism

Question 34

what are some quality control mechanisms?

Answer 34

there is no premature translation in the cytosol bc of processing is in the nucleus
no broken mRNA is translated bc 5’ cap and poly A are recognized by translational machinary

Question 35

what is nonsense-mediated mRNA decay?

Answer 35

there are stop codons in introns. if spliced correctly, stop codons and EJCs (placed whenever spliced) are gone.
if spliced incorrectly, Upf is trggered and mRNA is degraded