Block 1 090512 Translation And Genetic Code

Front 1

Compare the structure of ribosomes in prokaryotes and eukaryotes.

Back 1

Prokaryotes: Ribosome 70S = 30S (16S rRNA, 21 proteins ) + 50S (23S + 5S rRNA, 34 proteins)
Eukaryotes: 80S ribosome = 60S (5.8S + 28S + 5S, 50 proteins) + 40S (18S, 33 proteins

Front 2

What are the functions of ribosomes?

Back 2

1. synthesize protein
2. rRNA have enzymatic properties such as peptidyl transferase
3. form ribonucleoprotein complexes

Front 3

Compare and contrast the main structural components of prokaryotic versus eukaryotic mRNAs.

Back 3

Both: 5'UTR, 3'UTR, START codon (AUG) STOP codon (UGA,UAG,UAA)
Prokaryotes: Polycistronic, Have the Shine-Dalgarno sequence prior to start codon
Eukaryotes: Monocistronic, have 5' cap, and 3' poly A tail, and Kozak sequence around the start codon

Front 4

Describe the secondary and tertiary structure of tRNA in prokaryotes and eukaryotes.

Back 4

Prokaryotes and eukaryotes have the same structure:
2ndary: Forms a clover shape with 1 arm being the D loop and the other arm being the L loop. At the bottom loop is where the anticodons are located. There is a P at the 5'end and the AA attachment site at the 3' end
tertiary= looks more like a L and teh accpetor stemp has the 3' AA attachment site

Front 5

What are the functions of tRNA?

Back 5

1. binds to codon of mRNA and carries the specific AA
2. translates the genetic code of mRNA at anticodon loop
3. creates the acceptor stem by charging the CCA 3' end by aminoacyl linage to AA

Front 6

What is a charged tRNA molecule?

Back 6

When tRNA have the CCA 5' and allows for AAs to bind via aminoacyl binding

Front 7

What is the function of aminoacyl-tRNA synthetase in implementing the genetic code?

Back 7

It attaches a specific AA to its specific tRNA to aminoacyl-tRNA (charged) and there is 1 tRNA for every AA. Hardly ever any mis-pairings cause if wrong AA is added, it will be recognized at the active site and kicked off.

Front 8

Describe the aminoacyl-tRNA sythetase rxn.

Back 8

AA + ATP = AA-AMP + tRNA - AMP = aminoacyl-tRNA

(AMP is attached to the c-terminus of the AA) ( AA attached to the CCA 3' terminus of the tRNA

Front 9

Explain why the genetic code is degenerate?

Back 9

1. Many different codons (3 different bases) code for the same amino acid
2. 'wobble' = The 3rd base of codon exhibits nontraditional pairing with the 1sr base of the anticodon ex) U can bind to A or G
3) Modified base Inosine= can pair with any other base

Front 10

What direction is mRNA codons read?

Back 10

5' -->3'

Front 11

What direction is tRNA anticodons read?

Back 11

3'-->5'

Front 12

What are the stages of translation for both eukaryotes and prokaryotes?

Back 12

1.initation
2.elongation
3.termination

Front 13

Where does translation take place in prokaryotes and eukarotes?

Back 13

eukaryotes=cytoplasm
prokaryotes=cytoplasm, transcription and translation is simultaneous

Front 14

Compare and contrast initiation in translation of eukaryotes and prokaryotes.

Back 14

Prokaryotes:
1. IF-1 and IF-3 bind to 30S and IF-2-GTP + fMet-tRNA + RNA bind
2. IF-1 and 3 are released and 50S bind
3. GTP hydrolyzed and releases IF-2GDP
*Ribosomes know to bind there because of Shine-Dalgarno sequence that is just upstream to AUG start
Eukaryotes:
1. ternary cx(Met-tRNA + elF-2-GTP + eLF-1, eLF-1a, and eLF-3 binds to 40S = pre-initiation cx
2. pre-initiation cx binds to 5'cap of mRNA
3. subunits of eLF 4 bind
4. eIF-4 releases the cx and it scans for AUG towards the 3'end (ATP dependent)
5. once the start is found (by Kozak sequence) that eIF5 and 60S bind to form the 80S

Front 15

What are the prokaryotic initiating factors?

Back 15

IF-1, IF-2, IF-3

Front 16

What are the eukaryotic initiating factors?

Back 16

eIL-1, eIL-1a, eIL-2, eIL-3, eIL-4, eIL-5

Front 17

What elongation factors in eukaryotes and prokaryotes recruit AA-tRNA to A site and

Back 17

pro: EF-Tu
Euk: eEF-1a

Front 18

What is peptidyl transferase derived from in prokaryotes and eukaryotes?

Back 18

pro: 23S rRNA
euk: 28S rRNA

Front 19

What elongation facotrs in eukaryotes and prokaryotes translocate peptidyl tRNA and causes GTP hydrolysis?

Back 19

pro: EF-G
euk: eEF-2

Front 20

Describe the elongation stage.

Back 20

1.(f)Met-tRNA attached to P site
2. Depending on codon, the next AA-tRNA is carried to A site by (EF-Tu/eEF-1a)
3. AA-tRNA attaches to A site by hydrolysis of GTP (if correctly paired)
4. Peptidyl transferase forms the peptide bond
5. EF-G or eEF-2 stimulates GTP hydrolysis, translocation of peptidyl tRNA to the P site and the uncharged tRNA moves to the E site
6. bind of the next tRNA to the A site causes the uncharged tRNA to leave E site

Front 21

What elongation factors in prokaryotes and eukaryotes exchange GDP-Pi for GTP to activate EF-Tu or eEF-1a?

Back 21

pro: EF-Ts,
euk: eEF-1bg

Front 22

What direction do ply peptides grow?

Back 22

from amino end to carboxy end

Front 23

Describe termination of translation.

Back 23

1. stop codon moves into A site
2. release factors recognize stop codon
3. RFs bind to A site causes hydrolysis btwn C terminal AA of polypeptide chain and tRNA in P site

Front 24

What role do chaperone proteins play in translation?

Back 24

-stablize
-faciliate proper folding (primary AA sequence ultimately determines folding properties)

Front 25

What does streptomycin target?

Back 25

30S subunit to inhibit fmation of 70S initiation cx

Front 26

What does tetracycline target?

Back 26

30S subunit to inhibit binding of aminoacyl-tRNAs to the A site

Front 27

What does chloramphenicol target?

Back 27

50S subunit to inhibit peptidyl transferase rxn

Front 28

What does erythromycin target?

Back 28

50S subunit to inhibit translocation of peptidyl-tRNA from the A site to P site