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Bio 1113 > Chapter 17: From Gene to Protein > Flashcards

Chapter 17: From Gene to Protein Flashcards

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1
Q

What do tRNAs contain?

A

An anticodon

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2
Q

Overview of elongation of translation

A

Ribosome moves along mRNA adding amino acids to the growing polypeptide chain

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3
Q

3 steps of translation initiation

A
  1. rRNA in small subunit binds to the complementary sequence of mRNA (ribosomal binding site) helped by initiation factors
  2. Initiator tRNA binds to start codon
  3. Large subunit attaches to form translation initiation complex
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4
Q

Where does translation occur?

A

The cytoplasm

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5
Q

What do snRNPs do?

A

Recognize specific sequence at the end of introns and cuts out introns and joins exons back together

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6
Q

What does translation do?

A

Turns mRNA into protein

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7
Q

What makes up a snRNP (small nuclear ribonucleoprotein)?

A

snRNAs + proteins

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8
Q

What must happen to pre-mRNA before it can be transported to the cytoplasm for translation?

A

It must be modified in the nucleus with a 5’ cap and a 3’ Poly-A tail

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9
Q

How is transcription terminated in eukaryotes?

A

Poly(A) signal is the termination signal

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10
Q

Where are transcription and translation separated?

A

Eukaryotes

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11
Q

What helps RNA polymerase to recognize promoters in eukaryotic transcription? In bacteria?

A

In eukaryotes = basal transcription factors

In bacteria = sigma proteins

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12
Q

Enzymes which attach the amino acid to the tRNA

A

Aminoacyl-tRNA synthetases

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13
Q

What strand is the same as the RNA strand (except T and U) and is not read by RNA?

A

DNA coding strand

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14
Q

Overview of termination of transcription (bacteria)

A

Transcription proceeds until the polymerase reaches the terminator sequence which causes the enzyme to dissociate from the DNA

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15
Q

How is tRNA transcribed?

A

Transcribed from DNA template and folds to form a 3D structure

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16
Q

What does adding the 5’ cap and 3’ Poly-A tail do?

A
  1. Facilitate export from nucleus
  2. Protect from degradation in the cytoplasm by nucleases
  3. Help ribosomes attach to the 5’ end for translation
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17
Q

Overview of initiation of translation

A

Small unit of the ribosome with the initiator tRNA (methionine) already attached binds to the leader sequence of mRNA and scans for AUG and the large subunit binds and completes translation initiation complex

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18
Q

Enzyme adds 50-250 adenines to 3’ end

A

3’ Poly-A tail

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19
Q

What does transcription do?

A

Makes a single stranded copy of mRNA that can leave the nucleus. DNA —> mRNA

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20
Q

What do synthetases require to bring specific amino acids and tRNAs together?

A

ATP. Energy

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21
Q

What could happen if the 5’ cap and 3’ poly-a tail weren’t around to assist ribosomes?

A

Ribosomes could attach to any random AUG in the strand and not the start one on the 5’ end

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22
Q

What strand does the RNA read?

A

The DNA template strand

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23
Q

What does RNA polymerase do in elongation of transcription (bacteria)?

A
  1. Unwinds the helix and exposes 10-20 nucleotides at a time
  2. Synthesizes mRNA from 5’-3’ without the need of a primer
  3. Adds 50 nucleotides per second
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24
Q

What is the E ribosome site?

A

Where the empty tRNA exits

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25
Q

What are the 3 sites of a ribosome?

A

E, P, and A

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26
Q

How do synthetases work?

A

Their active site can only fit specific combinations of tRNA and amino acids (ensures anticodon brings in the correct amino acid)

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27
Q

Triplet which is complementary to codon on mRNA

A

Anticodon

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28
Q

What can holoenzymes do (bacteria)?

A

Recognize and bind to promoters in initiation of transcription

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29
Q

Overview of elongation of transcription (bacteria)

A

DNA is unwound and RNA polymerase creates a strand of mRNA which is complementary to the template strand of DNA. RNA polymerase synthesizes the mRNA in the 5’ to 3’ direction. Occurs at a rate of 50 bases per second

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30
Q

Where does transcription occur in eukaryotes?

A

The nucleus

31
Q

What can silent mutations create?

A

A splice site that isn’t supposed to be there (happens with Progeria)

32
Q

What typically happens to a single mRNA?

A

It is simultaneously translated by multiple ribosomes (polyribosomes)

33
Q

Overview of termination of translation

A

Ribosome hits a stop codon and the subunits separate and the polypeptide is released

34
Q

What must happen to a polypeptide for it to become a protein?

A

Correct secondary and tertiary folding

35
Q

What catalyzes the formation of peptide bonds?

A

rRNA

36
Q

What does polypeptide folding into a protein sometimes require?

A

Assistance of molecular chaperones

37
Q

What are the 3 steps of transcription?

A
  1. Initiation
  2. Elongation
  3. Termination
38
Q

Initial transcript in eukaryotes

A

pre-mRNA

39
Q

What are polyribosomes?

A

Multiple ribosomes on mRNA

40
Q

What does tRNA do?

A

Translates message from nucleic acids to amino acids

41
Q

What is tRNA with an amino acid attached called?

A

Charged

42
Q

What do tRNAs carry?

A

A specific amino acid

43
Q

What are some key players in translation?

A

tRNAs and ribosomes

44
Q

What does sigma do (bacteria)?

A

Guides RNA polymerase to start of a gene in initiation of transcription

45
Q

What is the A ribosome site?

A

Incoming (active) tRNA

46
Q

What 3 chemical modifications can occur after translation?

A
  1. Attachment of sugars, lipids, phosphate groups, etc
  2. Cleavage of polypeptide chain (like insulin)
  3. Interaction of multiple subunits (quaternary structure)
47
Q

Flexible base pairing in the 3rd position (not always A and U or C and G pairing in the third position which allows for less tRNAs)

A

Wobbles

48
Q

How long does it take to make a ribosome to make a polypeptide?

A

Less than a minute

49
Q

The part of eukaryotic genes that are coding segments

A

Exons

50
Q

Consist of a small and large subunit composed of protein and ribosomal RNA (rRNA)

A

Ribosomes

51
Q

Where can untranslated regions be found?

A

After the 5’ cap before the start codon and after the stop codon before the poly-a tail

52
Q

What doesn’t RNA polymerase need that DNA polymerase does?

A

A primer

53
Q

How is mRNA read?

A

3 bases at a time (codons) to build a polypeptide

54
Q

What are the 3 steps of translation termination?

A
  1. Elongation continues until a stop codon is reached
  2. A release factor (protein shaped like a tRNA) binds to the stop codon in the A site that causes the polypeptide to be released
  3. The translation assembly breaks apart
55
Q

What types of polymerases do eukaryotes have involved in transcription as opposed to bacteria?

A

3 main polymerases that each produce a certain type of RNA instead of just RNA polymerase

56
Q

What are the 3 steps of translation?

A
  1. Initiation
  2. Elongation
  3. Termination
57
Q

How many synthetases are there?

A
  1. 1 for each amino acid
58
Q

What is an untranslated region with base pairs AAUAAA found after the stop codon before the 3’ poly-a tail called?

A

Polyadenylation signal

59
Q

How does termination of transcription occur in bacteria?

A

RNA forms a hairpin loop and RNA polymerase releasees transcript

60
Q

What is the P ribosome site?

A

tRNA with growing polypeptide

61
Q

What differences are seen in the promoters of eukaryotic transcription as opposed to bacterial?

A

Promoters are more divers in eukaryotes (TATA box)

62
Q

What does translation elongation require?

A

Proteins (elongation factors) and energy

63
Q

What allows there to be less tRNAs than total codons?

A

Wobbles which are flexible base pairing in the 3rd position (not always A and U or C and G pairing in the third position which allows for less tRNAs)

64
Q

What two purposes do introns serve?

A
  1. Some introns contain sequences which play a role in regulating gene expression
  2. They allow for a single gene to code for more than one polypeptide (alternative RNA splicing)
65
Q

What is alternative RNA splicing?

A

Some exons can be left out of final transcript leading to more protein possibilities. More proteins can be made from the much smaller number of genes

66
Q

How do prokaryotic and eukaryotic ribosomes differ?

A

They are very similar in structure but subtle differences are exploited in medicine. Ex: tetracycline can inactivate bacterial ribosomes without harming human ribosomes

67
Q

Overview of initiation of transcription (bacteria)

A

Transcription factors and RNA polymerase bind to the promoter of the gene (which genes are transcribed is tightly controlled)

68
Q

What is RNA polymerase + sigma called (bacteria)?

A

Holoenzyme

69
Q

What do different sigma proteins do (bacteria)?

A

Bind promoters with different DNA sequences

70
Q

The part of eukaryotic genes that are noncoding DNA

A

Introns

71
Q

What is a spliceosome?

A

snRNPs that cut out introns and join exons back together

72
Q

How does translation elongation occur?

A

Amino acids are added one by one to growing polypeptide chain

73
Q

Modified guanine added to 5’ end

A

5’ cap

Bio 1113 (22 decks)

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