Translation

Question 1

Genetic Code

Answer 1

1) Info of bases in DNA and RNA to the structure of protein
2) Degenerate
- NOT 1:1, some amino acids encoded by more than one codon
3) Universal
4) Mitochondrial Genetic Code slightly different
5) 3rd base of code=silent bc encode same amino acid
6) Gives rise to polymorphic sequence difference in genes in humans

Question 2

Genes

Answer 2

1) DNA info for macromolecules (Protein, RNA)

- Blueprints

Question 3

mRNA

Answer 3

1) Messenger RNA
2) Required For protein Synthesis
3) carries info in the form of codons

Question 4

tRNA

Answer 4

1) Transfer RNA–>The translator
2) Required for Protein Synthesis
3) Uses anticodons
4) Aminoacyl-tRNA synthetase
- enzyme that attaches AA to NT sequence on 3’ end of tRNA=Charged tRNA
- Required ATP hydrolysis
- High Fidelity

Question 5

Open Reading Frames

Answer 5

1) mRNA=3 reading frames
- 2 are out of frame
- 1=ORF (open Reading Frame)=coding region–>part of the region that codes for proteins
2) Reading frames are open until STOP codon

Question 6

Stop codon

Answer 6

UAA
UAG
UGA

Question 7

mRNA structure

Answer 7

1) 5’ cap + 3’ polyA tail (only for eukaryotes)
2) UTR
- Untranslated region)
3) Start Codon
4) Coding Region
- aka ORF, cistron
- prokaryotes have multiple coding regions=polycistronic
5) Stop Codon

Question 8

Ribosomes

Answer 8

1) Required for Protein Synthesis
- catalyzes peptide bond formation
2) Built from several large structural rRNAs and many small proteins (rp’s)
3) Prokaryotic (E. coli)
- size=70s
- subunits=30s + 50s
4) Eukaryotic (Humans
- size=80s
- subuints= 40s+60s

Question 9

Silent Mutation

Answer 9

1) NT change does NOT alter protein sequence

Question 10

Missense Mutation

Answer 10

1) NT change alters 1 AA in protein sequence

2) Little effect on protein function in most cases

Question 11

Nonsense Mutation

Answer 11

1) NT change converts a sense codon to STOP codon
- NULL Mutation- ENDS translation and protein early
2) loss of function of proteins

Question 12

Read Through

Answer 12

1) NT change converts from a stop codon to a sense codon
- Fusion protein (extension)
2) Effect depends on position of next stop codon

Question 13

Frameshift

Answer 13

1) Gene mutation or splicing error that inserts or delete 1,2,4,or 5 NTs shifts out of reading frame
- insertions/deletions of multiple of 3s do not cause
2) Loss of function in protein due to termination premature

Question 14

Mutations can lead to disease by:

Answer 14

1) Potential to:
- destroy expression of fxn causing inherited disease
- disregulate cell growth (cancer)
- be fully tolerated
2) Often has environmental cause
- chemical mutagens
- carcinogen
- UV light
- Ionizing radiation
3) Can accumulate in DNA overtime
4) Can have some mechanisms to correct (dsDNA)

Question 15

Translation

Answer 15

1) 5’ to 3’ direction
2) mRNA–>Protein
- except tRNAs, structural RNAs, ribozymes
3) most energetically costly metabolic process in growing cells

Question 16

Requirements for Protein synthesis (TRANSLATION)

Answer 16

1) mRNA
2) tRNA (Charged)
3) Ribosomes
4) Translation factor (IFs or eIFs)
5) A lot of energy (ATP OR GTP)

Process requires High fidelity

Question 17

Translation: Initiation

Answer 17

Join ribosome, charged tRNA, and mRNA
No peptide bond formed
Many protein factors

Steps: (small subunit then big subunit)

1) eIFs brings the 1st charted tRNA (tRNA-met), GTP, and mRNA to 40s
2) eIFs attaches 40s to 60s=80s ribosome
3) 80s ribosome positioned at the start codon on mRNA (AUG)
4) tRNA-met goes to Psite
- all other tRNA following goes to A site

REGULATED by phosphorylation-no other step is

1) Ternary Complex formation
- eIF2 + GTP + tRNA-met
- +P=inhibits translation
2) mRNA recruitment (eIF4 +mRNA)
- requires ATP
- +P= stimulates translation

Question 18

Translation: ELongation

Answer 18

Ribosomes move 5’–>3’ along mRNA
Peptide Bonds made (first to last)
2 Protein Factors involved
NOT REGULATED

Steps:

1) eEF1 attaches to charged tRNA (not met) and delivers to A site
- requires GTP
- delivery stimulates Ribosome to catalyze peptidyl transferase= forms a connection between adjacent AA
2) eEF2 moves the ribosome 3 NT (1 codon)
- requires GTP
- ribosome moves ~5-40 codons/second (VERY SLOW)

Question 19

Translation: Termination

Answer 19

Stop codon in A site
Hydrolysis to free protein
1 protein factor-mimics tRNA

Steps:

1) Release factors recognize stop codon in A site
2) eRF1 stimulates ribosome to catalyze peptidyl transfer but no AA present
3) Instead 60s uses H2O for Nucleophilic Attack
- hydrolyzes peptidyl chain from tRNA
- release protein
4) Other RFs cause dissociation of complex (mRNA + tRNA)

Question 20

Inhibitors of prokaryotic protein synthesis

Answer 20

Common antibiotics

1) Tetracycline
2) Erythromycin
3) CHloramphenicol
4) Streptamycin/Neomycin/Gentamycin

Question 21

Tetracycline

Answer 21

1) inhibits prokaryotic protein synthesis
- Binds 30s
- Prevents aminoacyl-tRNA binding in A site
2) Reversible

Question 22

Erythromycin

Answer 22

1) Inhibits prokaryotic protein synthesis

- Blocks peptidyl transferase activity in 50s

Question 23

Chloramphenicol

Answer 23

1) Inhibits prokaryotic protein synthesis
- blocks amnoacyl-tRNA binding to 50s
- inhibits eukaryotic mitochondrial translation (rarely)

Question 24

Streptamycin/Neomycin/Gentamycin

Answer 24

1) Inhibits prokaryotic protein synthesis
- binds 30s
- cause codon misreadings that lead to disincorporation of AA’s result in nonfxnal proteins

Question 25

Inhibitor os eukaryotic protein synthesis

Answer 25

1) Diptheria Toxin
2) Cycloheximide
3) Ricin

Question 26

Diptheria Toxin

Answer 26

1) Inhibits eukaryotic protein synthesis
- released by corynebacterium diphtheria
- uses NAD+ to ADP ribosylate eEF2
- Blocks 80s translocation

Question 27

Cycloheximide

Answer 27

1) Inhibits eukaryotic protein synthesis
- released by streptomycin griseus
- inhibits 80s translocation
- freezes ribosomes on mRNA

Question 28

Ricin

Answer 28

1) Inhibits eukaryotic protein synthesis
- From castor bean
- N-Glycosidase enzyme that blocks eEF1/2
- Removes single ADENINE base from ribosome