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C Bio > tRNA, rRNA & Translation (10) > Flashcards

tRNA, rRNA & Translation (10) Flashcards

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Biology 101 flashcards
1
Q

RNA in the nucleus

A 
hnRNA
mRNA
rRNA
tRNA
snRNA
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2
Q

RNA in the cytoplasm

A

mRNA
tRNA
rRNA

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3
Q

RNA pol II

A

makes hnRNA

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4
Q

RNA pol I

A

makes rRNA

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5
Q

RNA Pol III

A

makes tRNA & 5S rRNA

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6
Q

tRNA function

A

translates mRNA into AA of the polypeptide

carrier of AAs

bind to codon

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7
Q

what causes the 3D shape in tRNA?

A

internal complementarity

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8
Q

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

A

some uridines are converted to dihydrouridine or pseudouridine

some nucleotides are methylated

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

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9
Q

where is the AA attachment site?

A

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

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10
Q

What significant about the sequence of the AA attachment site?

A

not encoded in DNA, sequence is added at the end

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11
Q

anticodon

A

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

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12
Q

why does tRNA have loops & stems?

A

enables the molecule to fit into the ribosome

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13
Q

what does tRNA serve as an adaptor to?

A

AA to tRNA

codon to anticodon

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14
Q

genetic code

A

consists of grps of 3 of 3 nucleotides called codons

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15
Q

how many diff codons are there?

A

64 (4^3)

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16
Q

how many diff AAs are there?

A

20

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17
Q

what provides the redundancy in the genetic code

A

64 codons for 20 AAs

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18
Q

wobble position & what does it create

A

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

degenerate code

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19
Q

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

A

wobble position

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20
Q

Why is there a wobble position?

A

buffers any deficiencies or errors to prevent anything from going wrong

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21
Q

what is the role of aminoacyl-tRNA synthetase?

A

charges/activates tRNA by adding the correct AA

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22
Q

what are the steps in aminoacyl tRNA synthetase activating tRNA?

A
  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

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23
Q

How does aminoacyl tRNA synthetase correctly add AAs?

A

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

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24
Q

aminoacyl tRNA

A

complex of AA & tRNA

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25
Q

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

A

not a 1:1

a 1:1

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26
Q

how many tRNA genes are in humans?

A

1300

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27
Q

why do humans have so many tRNA genes?

A

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

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28
Q

What is the size of a eukaryotic ribosome?

A

80S

lrg subunit: 60S
small subunit: 40S

29
Q

What is the composition of ribosomes?

A

PROs & rRNA

30
Q

where are ribosomes assembled?

A

nucleus

31
Q

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

A

3 diff rRNA + 49 PROs = 60S

32
Q

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

A

18S + 33 PROs = 40S

33
Q

what does internal base pairing in rRNA produce?

A

secondary & tertiary structure

34
Q

ribosome structure is both ___ & ___

A

structural & catalytic

35
Q

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

A

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

36
Q

What modifications occur in the RNA encoding 3 rRNAs?

A

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

28S
18S
5.8S

37
Q

What RNA gene is outside the nucleus?

A

5S

38
Q

where does ribosome assembly occur & how is it done?

A

nucleolus

bringing together the 45S transcript, processing enzymes & PROs

39
Q

How & where do the rRNA genes occur?

A

appear in multiple copies in clusters in the nucleolar organizer regions

40
Q

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

A

45S

41
Q

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

A

removal of spacers & base modifications

done by snoRNPs & other PROs

42
Q

How is 5S rRNA made?

A

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

43
Q

nucleolar organization region rRNA?

A

18S, 28S & 5.8S

44
Q

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

A

pol III (5S)

45
Q

ribosome role in translation

A

guide tRNAs along mRNA

46
Q

what are the modifications of mRNA?

A 
5' cap 
5' UTR
Coding region with start & stop codons
3' UTR
PolyA region
47
Q

which subunit is assoc with IFs?

A

small subunit

48
Q

what is the starting codon &AA?

A

MET

49
Q

where does ribosome machinery assemble?

A

mRNA strand

50
Q

how is the reading frame properly established?

A

properly aligning the 1st codon

51
Q

shine dalgarno sequence & how is it recognized?

A

ribosome binding site upstream of AUG in prokaryotes

subunit recognizes the special sequence by base pairing

52
Q

what size is the small subunit rRNA in prokaryotes?

A

16S

53
Q

What facilitates tRNA to bind to the mRNA?

A

hydrolysis of GDP

54
Q

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

A

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

55
Q

What are the diffs in initiation in eukaryotes & prokaryotes?

A

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

56
Q

When does an E burning step occur in translation?

A

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

57
Q

peptidyl transferase

A

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

58
Q

what enables the tRNA to exit the ribosome?

A

AA bound to polypeptide chain

59
Q

What occurs in initiation of translation? (details)

A
  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
60
Q

What occurs in elongation of translation? (details)

A
  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
61
Q

What occurs in termination in translation?

A

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

62
Q

what are the steps in initiation?

A
  1. Attachment of the small subunit
  2. Bring in 1st AA
  3. Complete initiation complex
63
Q

what are the steps in elongation?

A
  1. Selection
  2. Peptide bond formation (peptidyl transferase activity)
  3. Translocation
  4. Release of de-acylated tRNA
64
Q

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

A

PRO mimics a tRNA anticodon

same size of tRNA so it can have access

65
Q

what are the diffs in termination in prokarytoes & eukaryotes?

A

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

66
Q

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

A

eIFs & polyA binding PRO

67
Q

how is tetracycline effective?

A

binds to the small subunit

68
Q

how is streptomycin effective?

A

binds to the 16S rRNA & inhibits initiation

C Bio (30 decks)

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