Genetic Code and Translation

Question 1

What is the order of transcription, translation, and mRNA degradation in prokaryotes

Answer 1

they are simultaneous occurrences

Question 1

In eukaryotes where do transcription and translation occur

Answer 1

transcription - nucleus
translation - cytoplasm

Question 2

Why does mRNA last longer in eukaryotes

Answer 2

in prokaryotes all steps occur in the same location simultaneously, in eukaryotes transcription and translation occur in different parts of the cell so mRNA exists for longer in eukaryotes

Question 3

What researchers led to the “one gene one collinear protein” conclusion

Answer 3

Beadle and Tatum

Question 4

What bond holds amino acids together

Answer 4

peptide bond (carboxyl of one bonded to amino of the other)

Question 5

What code does the genetic code follow

Answer 5

triplet code
4^3 = 64 possible codons

Question 6

How were codons discovered

Answer 6

homopolymers and copolymers were tested and were found to produce polypeptides with different amino acids

Question 7

How many codons are there

Answer 7

64

Question 8

How many of the 64 codons are stop codons

Answer 8

3

Question 9

What does it mean when saying the genetic code is degenerate

Answer 9

some amino acids are specified by more than one codon

Question 10

What 2 amino acids are specified by only one codon

Answer 10

methionine (start) and tryptophan

Question 11

Why does degeneracy occur in the genetic code

Answer 11

the binding at the third codon position is flexible
- known as the wobble position

Question 12

How does wobble occur in translation (think tRNA modification)

Answer 12

since tRNA can be modified at the nucleotide level, nucleotides can be substituted for other nucleotides and create wobble

Question 13

What is the basics of the wobble hypothesis

Answer 13

nonstandard pairings can occur at the third position of a codon

Question 14

What is a nickname for the ribosome

Answer 14

RNA machine - plays a role in protein synthesis, including the formation of peptide bonds between amino acids

Question 15

What are the 4 important macromolecules of translation

Answer 15

1. ribosomes
2. amino acid activating enzymes
3. tRNA molecules
4. soluble proteins involved in initiation, elongation and termination

Question 16

What is the function of aminoacyl tRNA synthetase

Answer 16

charges the tRNA molecule with its specific amino acid

Question 17

What is the 2 step reaction between the amino acid and tRNA via aminoacyl tRNA synthetase

Answer 17

1. amino acid reacts with ATP to our aminoacyl AMP
2. amino acid is transferred to tRNA and AMP is released

Question 18

How to tRNAs work

Answer 18

hold the anticodon for the codon of mRNA

Question 19

What is another term for translation

Answer 19

protein synthesis

Question 20

What is required to initiate translation

Answer 20

mRNA, large and small ribosomal subunits, initiation factors, and GTP

Question 21

What is the initiation complex of translation in prokaryotes

Answer 21

Shine Dalgarno sequence

Question 22

Where is the complement to the Shine dalgarno sequence held

Answer 22

in the 16S component of the 30S small ribosomal subunit

Question 23

What is the Shine Dalgarno sequence

Answer 23

UAAGGAGGU

Question 24

How does the small subunit bind first to prokaryotic mRNA in translation, without the binding of the large subunit

Answer 24

IF-3 binds to the large unit, preventing it from binding, causing only the small subunit to bind (has complementary sequence to Shine Dalgarno)

Question 25

What positions fMet-tRNA over the start codon

Answer 25

IF-1 and IF-2

Question 26

What makes up the 30S initiation complex

Answer 26

fMet-tRNA + 30S small subunit + IF2-GTP + IF-1 + IF-3

Question 27

How does the large subunit then attach to the mRNA in prokaryotic translation initiation

Answer 27

IF-3 dissociates

Question 28

How are the IF-2 and IF-1 factors dissociated from the initiation complex in prokaryotic translation

Answer 28

GTP is hydrolized into GDP and dissociates the remaining IF factors

Question 29

What is the final complex at the start of prokaryotic translation called

Answer 29

the 70S complex (think of the overall subunits and complex of prokaryotic ribosomes)

Question 30

What is the E site

Answer 30

exit site

Question 31

What is the P site

Answer 31

peptidyl site

Question 32

What is the A site

Answer 32

aminoacyl site

Question 33

What is the difference in methionine between prokaryotes and eukaryotes

Answer 33

prokaryotes = fMet eukaryotes = Met (not formylated)

Question 34

What is the difference about the initiation complex location in prokaryotes and eukaryotes

Answer 34

prokaryotes = Shine Dalgarno eukaryotes = initiation complex binds at 5' cap and scans inwards to find first AUG codon

Question 35

What is the sequence involved in eukaryotic translation

Answer 35

Kozak sequence

Question 36

What is the purpose of the Kozak sequence

Answer 36

influence the efficiency of which AUG in the vicinity is used to begin translation

Question 37

What happens between the poly A tail and the 5' cap structure in eukaryotic mRNA translation

Answer 37

the mRNA strand curls and proteins attached to the poly A tail interact with the proteins bound to the 5' cap to create a cap binding protein complex

Question 38

What is the cap binding protein complex

Answer 38

when binding proteins on the poly A tail and binding proteins on the 5' cap of eukaryotic mRNA interact during initiation of translation

Question 39

What is the Kozak sequence

Answer 39

5' - C[A/G]NCAUG - 3'

Question 40

Where does fMet - tRNA first attach in translation elongation

Answer 40

the P site (skips A site)

Question 41

What two things come together to form a complex as the second tRNA molecule comes into translation elongation

Answer 41

Ef-Tu and GTP bind to charged tRNA to form a complex - enters the A site of the ribosome (the second tRNA)

Question 42

What happens when the SECOND charged tRNA in elongation binds to the A site in translation

Answer 42

GTP is cleaved to GDP and the Ef-Tu complex is released

Question 43

Explain the basics of elongation in translation

Answer 43

- first tRNA binds to the P site - second tRNA binds to Ef-Tu and GTP to form a complex, binds to the A site, and released the complex - peptide bond forms between the amino acids in the P and A sites - the ribosome moves down the mRNA strand to synthesize the amino acid chain *tRNA moves from the A site to P site to E site (with the first tRNA starting at the P site)

Question 44

Where does tRNA go after being used in translation

Answer 44

released into cytoplasm

Question 45

What specifically in the large subunit catalyzes the formation of peptide bonds

Answer 45

rRNAs

Question 45

Which subunit catalyzes the peptide bond formation between amino acids

Answer 45

large subunit

Question 46

What is needed in order for translocation (movement of tRNA from one site to the next) to occur

Answer 46

the Ef-Tu GTP complex

Question 47

What does it mean for tRNA to be "charged"

Answer 47

has a bound amino acid

Question 48

What direction does the ribosome move along mRNA in translation

Answer 48

5' - 3'

Question 49

In what direction does growth of the polypeptide occur

Answer 49

N-teminal to C-terminal

Question 50

Which site on the ribosome contains the growing peptide chain

Answer 50

the P site

Question 51

Are there notable differences in translation elongation between prokaryotes and eukaryotes

Answer 51

no - they are very similar

Question 52

When does termination occur in translation

Answer 52

when a stop codon is encountered at the A site of the ribosome

Question 53

Why does translation stop when a stop codon is encountered at the A site

Answer 53

because there are no corresponding tRNAs that match stop codons

Question 54

What happens when a stop codon is encountered instead of tRNA binding

Answer 54

a release factor binds (RF)

Question 55

What does RF-1 recognize

Answer 55

UAG and UAA

Question 56

What does RF-2 recognize

Answer 56

UAA and UGA

Question 57

What does the binding of RF-1 and RF-2 do to the translation process

Answer 57

alters the activity of peptidyl transferase and the amino acid chain is released, termination translation

Question 58

What factors assist in dismantling the ribosomal complex in translation post termination

Answer 58

RF-3 and GTP

Question 59

What is the difference between prokaryotic and eukaryotic termination of translation

Answer 59

they are very similar - release factors are symbolized as eRF-1 and eRF-2 in eukaryotes

Question 60

What enzyme attaches amino acids to tRNAs in tRNA charging of translation

Answer 60

aminoacyl-tRNA synthetases

Question 61

What is the energy source used to bind amino acids to tRNAs

Answer 61

ATP

Question 62

What is the function of elongation factor Tu

Answer 62

binds GTP and charged tRNA - brings charged tRNA to A site on ribosome

Question 63

What is the function of elongation factor Ts

Answer 63

regenerates active elongation factor Tu

Question 64

What is the function of elongation factor G

Answer 64

stimulates translocation of ribosome to next codon

Question 65

What is the function of GTP

Answer 65

provides energy

Question 66

What is the function of the 23S rRNA in the large ribosomal subunit

Answer 66

form peptide bonds between amino acids in the P and A sites

Question 67

What step of translation does chloromycetin inhibit

Answer 67

formation of peptide bonds

Question 68

What step of translation does erythromycin inhibit

Answer 68

translocation of mRNA along ribosome

Question 69

What step of translation does neomycin inhibit

Answer 69

interactions between tRNA and mRNA

Question 70

What step of translation does streptomycin inhibit

Answer 70

initiation of translation

Question 71

What step of translation does tetracycline inhibit

Answer 71

binding of tRNA to ribosome

Question 72

What step of translation does paromomycin inhibit

Answer 72

validation of mRNA-tRNA match

Question 73

What are some neurological diseases associated with translation

Answer 73

amyotrophic lateral sclerosis frontotemproal dementia spinal musclar atrophy alzheimers parkinsons huntingtons autism down syndrome