tRNA, rRNA & Translation (10)

Question 1

RNA in the nucleus

Answer 1

hnRNA
mRNA
rRNA
tRNA
snRNA

Question 2

RNA in the cytoplasm

Answer 2

mRNA
tRNA
rRNA

Question 3

RNA pol II

Answer 3

makes hnRNA

Question 4

RNA pol I

Answer 4

makes rRNA

Question 5

RNA Pol III

Answer 5

makes tRNA & 5S rRNA

Question 6

tRNA function

Answer 6

translates mRNA into AA of the polypeptide

carrier of AAs

bind to codon

Question 7

what causes the 3D shape in tRNA?

Answer 7

internal complementarity

Question 8

What are the chemical modifications of tRNA after transcription? & why is this done?

Answer 8

some uridines are converted to dihydrouridine or pseudouridine

some nucleotides are methylated

required for correct 3D shape & chemistry to provide the correct function

Question 9

where is the AA attachment site?

Answer 9

AA attachment site is located at the top of the tRNA, the Adenine in the CCA sequence at the 3’ end

Question 10

What significant about the sequence of the AA attachment site?

Answer 10

not encoded in DNA, sequence is added at the end

Question 11

anticodon

Answer 11

3 sequential nucleotides in the middle of the loop which function in the recognition of the complementary mRNA codon

Question 12

why does tRNA have loops & stems?

Answer 12

enables the molecule to fit into the ribosome

Question 13

what does tRNA serve as an adaptor to?

Answer 13

AA to tRNA

codon to anticodon

Question 14

genetic code

Answer 14

consists of grps of 3 of 3 nucleotides called codons

Question 15

how many diff codons are there?

Answer 15

64 (4^3)

Question 16

how many diff AAs are there?

Answer 16

20

Question 17

what provides the redundancy in the genetic code

Answer 17

64 codons for 20 AAs

Question 18

wobble position & what does it create

Answer 18

The 3rd position of the anticodon can sometimes bind to non-complementary nucleotides

degenerate code

Question 19

Different nucleotide in a codon coding for the same AA differs in the ___

Answer 19

wobble position

Question 20

Why is there a wobble position?

Answer 20

buffers any deficiencies or errors to prevent anything from going wrong

Question 21

what is the role of aminoacyl-tRNA synthetase?

Answer 21

charges/activates tRNA by adding the correct AA

Question 22

what are the steps in aminoacyl tRNA synthetase activating tRNA?

Answer 22

1. AA & ATP bind to enzyme
2. 2 Ps are released, AMP binding activates the AA
3. tRNA binds to synthetase, AA covalently bonds to the tRNA & AMP is released
4. Charged tRNA is released with AA

AA is added to the CCA end

Question 23

How does aminoacyl tRNA synthetase correctly add AAs?

Answer 23

recognizes unique parts of each tRNA (adapter function), assures correct anticodon

Question 24

aminoacyl tRNA

Answer 24

complex of AA & tRNA

Question 25

What sort of relationship exists b/w tRNAs & codons? & tRNA genes with tRNAs?

Answer 25

not a 1:1 a 1:1

Question 26

how many tRNA genes are in humans?

Answer 26

1300

Question 27

why do humans have so many tRNA genes?

Answer 27

more copies of the genes will produce more tRNA transcripts humans require a lot of tRNA to build the PROs that they're composed of

Question 28

What is the size of a eukaryotic ribosome?

Answer 28

80S lrg subunit: 60S small subunit: 40S

Question 29

What is the composition of ribosomes?

Answer 29

PROs & rRNA

Question 30

where are ribosomes assembled?

Answer 30

nucleus

Question 31

what is the composition of the large subunit of a prokaryote?

Answer 31

3 diff rRNA + 49 PROs = 60S

Question 32

what is the composition of the small subunit of a eukaryote?

Answer 32

18S + 33 PROs = 40S

Question 33

what does internal base pairing in rRNA produce?

Answer 33

secondary & tertiary structure

Question 34

ribosome structure is both ___ & ___

Answer 34

structural & catalytic

Question 35

what are the post-transcriptional modifications of tRNA & rRNA?

Answer 35

a) RNA with conventional base-pair folding b) RNA with nonconventional base-pair interactions c) Structure of actual RNA molecule

Question 36

What modifications occur in the RNA encoding 3 rRNAs?

Answer 36

large 45S rRNA is copied & cut into 3 rRNAs: 28S 18S 5.8S

Question 37

What RNA gene is outside the nucleus?

Answer 37

5S

Question 38

where does ribosome assembly occur & how is it done?

Answer 38

nucleolus bringing together the 45S transcript, processing enzymes & PROs

Question 39

How & where do the rRNA genes occur?

Answer 39

appear in multiple copies in clusters in the nucleolar organizer regions

Question 40

what rRNA gene is responsible for the tree appearance of the tRNA?

Answer 40

45S

Question 41

How are 45S transcripts modified? & what does this?

Answer 41

removal of spacers & base modifications done by snoRNPs & other PROs

Question 42

How is 5S rRNA made?

Answer 42

transcribed by RNA pol III & shipped to the nucleolus post synthesis

Question 43

nucleolar organization region rRNA?

Answer 43

18S, 28S & 5.8S

Question 44

what polymerase isn't involved in translation of NOR rRNA?

Answer 44

pol III (5S)

Question 45

ribosome role in translation

Answer 45

guide tRNAs along mRNA

Question 46

what are the modifications of mRNA?

Answer 46

``` 5' cap 5' UTR Coding region with start & stop codons 3' UTR PolyA region ```

Question 47

which subunit is assoc with IFs?

Answer 47

small subunit

Question 48

what is the starting codon &AA?

Answer 48

MET

Question 49

where does ribosome machinery assemble?

Answer 49

mRNA strand

Question 50

how is the reading frame properly established?

Answer 50

properly aligning the 1st codon

Question 51

shine dalgarno sequence & how is it recognized?

Answer 51

ribosome binding site upstream of AUG in prokaryotes subunit recognizes the special sequence by base pairing

Question 52

what size is the small subunit rRNA in prokaryotes?

Answer 52

16S

Question 53

What facilitates tRNA to bind to the mRNA?

Answer 53

hydrolysis of GDP

Question 54

how does the shortening of the polyA tail determine the half-life?

Answer 54

will weaken the eIFS & cause the molecule to de-circularize

Question 55

What are the diffs in initiation in eukaryotes & prokaryotes?

Answer 55

There is an eIF with GTP that becomes hydrolyzed, GTP is separate in prokaryotes mRNA is capped, looks for cap to initiate translation, eIFs cause the polyA tail to loop on itself so its close to the 5’ cap, mRNA isn't capped in prokaryotes Indicator codon is directed by the eIF on the cap scanning for the first AUG & in prokaryotes shine-dalgarno signifies the 1st codon

Question 56

When does an E burning step occur in translation?

Answer 56

tRNA is delivered to the A site & GTP --> GDP + P

Question 57

peptidyl transferase

Answer 57

ribozyme on the large rRNA, covalently binds the AA in the A site to the AA in the P site in translation

Question 58

what enables the tRNA to exit the ribosome?

Answer 58

AA bound to polypeptide chain

Question 59

What occurs in initiation of translation? (details)

Answer 59

1. Attachment of the small subunit (with IFs complex) Small subunit, GTP, IFs/eIFs Small subunit binds to IFs/eIFs & GTP binds to IFs/eIFs & then binds to small subunit Slides along molecule looking for shine-dalgarno 2. Bring in 1st AA fMet in prokaryotes of initiator codon in Eukaryotes 3. Complete initiation complex large subunit attaches, IFs/eIFs are lost, GTP GDP

Question 60

What occurs in elongation of translation? (details)

Answer 60

1. Selection anticodon binds with correct codon 1st tRNA binds to the T site & GTP GDP + P EF brings charged tRNA to the site After the very 1st tRNA, tRNA is delivered into the A site & GTP GDP + P An elongation factor removes GDP from tRNA & replaces it with a GTP recharges the tRNA 2. Peptide bond formation (peptidyl transferase activity) AA in A site covalently bonds (peptide bond) to the AA in the P site performed by peptidyl transferase (ribozyme of large subunit) AA leaves tRNA in the P site 3. Translocation Ribosome moves down 1 codon due to an elongation factor Empty tRNA shifts to the E site & peptide chain is in the P site AA bound to the chain enables tRNA to exit 4. Release of de-acylated tRNA

Question 61

What occurs in termination in translation?

Answer 61

Reach stop codon Release factor is inserted (mimics tRNA anticodon) Polypeptide is released & subunits fall apart

Question 62

what are the steps in initiation?

Answer 62

1. Attachment of the small subunit 2. Bring in 1st AA 3. Complete initiation complex

Question 63

what are the steps in elongation?

Answer 63

1. Selection 2. Peptide bond formation (peptidyl transferase activity) 3. Translocation 4. Release of de-acylated tRNA

Question 64

how does the RF manage to get inserted in the ribosome?

Answer 64

PRO mimics a tRNA anticodon | same size of tRNA so it can have access

Question 65

what are the diffs in termination in prokarytoes & eukaryotes?

Answer 65

Same in Eukaryotes & Prokaryotes except: 2 release factors in eukaryotes & 3 in prokaryotes

Question 66

what enables the 5' cap to attach to the polyA tail?

Answer 66

eIFs & polyA binding PRO

Question 67

how is tetracycline effective?

Answer 67

binds to the small subunit

Question 68

how is streptomycin effective?

Answer 68

binds to the 16S rRNA & inhibits initiation