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Genetics > 6. Translation > Flashcards

6. Translation Flashcards

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0
Q

start codon

A

AUG (met)

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1
Q

codons

A

3 nucleotides long
each codon represents one AA

(AAs can be represented by many codons)

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2
Q

stop codon

A

UGA
UAG
UAA

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3
Q

direction code is being read for translation?

A

5’ to 3’

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4
Q

tRNA

A

used to read the codons on the mRNA

uses anticodon to base pair with a codon on mRNA

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5
Q

5’ position of the tRNA on the anticodon

A

wobble position

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6
Q

inosine

A

modified base (I)

created by deamination of guanine
when present in the wobble position of the anticodon, can recognize:
U or C in euks
U, C, or A of proks

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7
Q

aminoacyl-tRNA synthetase

A

activates an AA for protein synthesis in 2 steps

  1. uses ATP to adenylate the AA
  2. creates an amino-acyl tRNA

AA is now linked to tRNA via carboxy, makes HIGH ENERGY ester linkage

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8
Q

once tRNA is activated w/AA?

A

can bind to mRNA complement

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9
Q

hydrolytic editing

A

if wrong AA is added to tRNA, they will bind incorrectly to the synthetase and then bind the editing site

in the editing site, the incorrect AA will be removed an the correct one added

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10
Q

translation occurs? (what direction)

A

N to C terminus

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11
Q

bacterial v. eukaryotic ribosomes

A

bacterial: 50s, 30s, 70s
eukaryotic: 60s, 40s, 80s

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12
Q

each ribosome contains?

A

binding site for mRNA

3 for tRNA: A site (aminoacyl-tRNA), P site (peptidyl RNA), E site (exit)

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13
Q

elongation step 1

A

aminoacyl-tRNA binds A site

used up RNA leaves through E site

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14
Q

elongation step 2

A

new peptide bond formed (peptidyl transferase activity)

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15
Q

elongation step 3

A

large subunit translocates relative to small subunit–leaving 2 tRNAs in hybrid site; P site & E/P site

16
Q

elongation step 4

A

small subunit translocates a distance of 3 nucleotides to catch up with the large subunit, carrying mRNA with it

ribosome now has an empty A site (ready to bind another aminoacyl-tRNA)

17
Q

elongation factors

A

EF1=EF-tu

EF2=EFG

18
Q

what do elongation factors do?

A

provide free energy to drive rxn fwd

use GTP hydrolysis as signal

19
Q

EF1

A

bound to GTP, helps delive an actiated tRNA to an empty A site
proofreading pause to ensure that the anticodon match is correct

20
Q

if correct match

A

GTP is hydrolyzed, tRNA is delivered

21
Q

if incorrect match

A

no GTP hydrolysis

elongation cannot continue until there is a proper match

22
Q

16S RNA of the small ribosomal subunit

A

helps recognize proper binding between the codon and anti-codon

forms an H bond network with the first nucleotide or a correct codon-anticodon pairing

23
Q

after you get proper binding?

A

EF2 bound to GTP binds to ribosome causing the large ribosomal subunit to ratchet forward

hydrolysis of GTP causes the small ribosomal subunit to follow, freeing up the A site

24
Q

initiation: eIF2

A

GTP bound protein that uses GTP hydrolysis

helps chaperone the tRNA to bind the small ribosomal subunit–>binds 5’ cap of mRNA to be translated–>initiator tRNA will then scan 5’ to 3’ looking for Met in appropriate context

25
Q

once the consensus recognition sequence encountered?

A

hydrolysis of GTP on eIF2
removal of eIF2
recruitment of large ribosomal subunit
elongation can now begin

26
Q

termination

A

stop codon enters A site, releasing factor protein mimics the function of a tRNA and binds to the codon, triggering termination

27
Q

example of molecular mimicry?

A

releasing factor protein

mimics shape and function of tRNA, but serves to terminate translation

28
Q

polyribosomes

A

many ribosomes working together on the same mRNA molecule to synthesize proteins

29
Q

final protein production depends on efficiency of what?

A
  1. initiation of transcription
  2. generation of primary transcript
  3. generation of mRNA that can get transported into cytoplasm for translation
30
Q

points of regulation of translation (4)

A
  1. binding of small molecule to part of mRNA secondary structure (riboswitch), induces autolytic ribozyme activity
  2. riboswitch causes structural rearrangment of RNA, blocking translation initiation
  3. thermosensor: increased temp can alter the structure of some pathogenic RNA by melting AT rich regions; allows for translation of pathogenic proteins
  4. antisense RNA: can basepair with a specific mRNA, blocking the start codon and thus translation

Genetics (42 decks)

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