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Miscellaneous > MCB Lecture 20 Protein Synthesis > Flashcards

MCB Lecture 20 Protein Synthesis Flashcards

0
Q

What is mRNA?

A

Messenger RNA

Translated into proteins

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1
Q

What is rRNA?

A

Ribosomal RNA that makes up the structure of ribosomes

Untranslated

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2
Q

What is tRNA?

A

Translational RNA
Delivers codons and amino acids
Untranslated

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3
Q

What is snRNA?

A

Small nuclear RNA
Makes up the spliceosome
Removes introns from hnRNA

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4
Q

Differentiate between RNAP in prokaryotes and eukaryotes.

What are the similarities and differences?

A

There is only one in prokaryotes and three in eukaryotes

The structure of eukaryotic RNAPs are quite similar to prokaryotic ones, except they have more associated subunits

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5
Q

How do RNAP differ from DNApol?

A

They do not have proofreading mechanisms

Ey do not require primers

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6
Q

What is the function of RNA pol I?

A

Synthesised ribosomal RNA

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7
Q

What is the function of RNApol II?

A

Synthesised mRNA

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8
Q

What is the function of RNApol III ?

A

Synthesises tRNA

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9
Q

How do promoter regions differ in prokaryotes and eukaryotes?

A

There is much more variation in eukaryotic promoter regions

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10
Q

What makes up the transcription preinitiation complex?

A

RNApol
TFIID: TBP and TAF
And the other four GTFS

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11
Q

What are GTFs?

How many types are there?

A

General transcription factors

There are 5

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12
Q

What is TFIID comprised of?

A

TBP and TAF

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13
Q

What is TBP?

Where does it have a role?

A

TATA binding protein

It forms part of the preinitiation complex in transcription by binding it to the promoter region

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14
Q

What is TAF?

What does it do/associate with?

A

TBP associated factor

Makes up TFIID which has a role in the pre-initiation complex

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15
Q

Describe the process of the preinitiation complex formation

A
  1. TBP and TAF combine with RNA pol
  2. TBP binds to the TATA box in the promoter
  3. The four other GTF bind
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16
Q

Describe the function of the mediator

A

The mediator connects the RNA Pol to the activator and thus enhancer region of the DNA

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17
Q

Describe the function of the activator

A

The activator binds to the enhancer region upstream from the promoter and thus increases gene expression

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18
Q

What do the Chromatin Modifying Proteins do?

Name one

A

SAGA is an example of chromatin modifying proteins

It moves the nucleosomes out of the way so that transcription can occur

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19
Q

Describe how the enhancer, activator and mediator work together

A

Enhancer is a region of DNA upstream from the promoter
The activator is a molecule that binds to the enhancer to increase gene expression
The mediator connects the activator and the RNA pol

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20
Q

Which enzyme opens up the DNA strands (like helicase) in transcription?

A

TFIIH

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21
Q

What happens to the preinitiation complex when elongation starts?

A

The GTFs dissociate from the RNA Pol

22
Q

What is the CTD of RNApol? What is special about it?

A

The C terminal domain
It has had it’s phosphorylation changed
Ser-5 -> ser-2

23
Q

Transcription elongation requires the recruitment of many other …

A

eIF

Elongation initiation factors

24
Q

What happens when specific termination sequences are transcribed?

A

When the termination sequence is transcribed, certain proteins are recruited and bound to the sequence and the mRNA strand is cleaved from the RNA pol

25
Q

What is CstF?

A

Cleavage stimulation factor

26
Q

What is CPSF?

A

Cleavage and Polyadenylation Stimulating Factor

27
Q

What is PAP

A

Poly adenylase polymerase

28
Q

What is PABP?

A

Poly adenylase binding protein

29
Q

How does the mRNA get cleaved from the RNAP?

What happens next?

A
  1. Specific sequence is transcribed
  2. CstF and CPSF bind to the mRNA
  3. mRNA is cleaved
  4. PAP adds nucleotides to the 3’ end
  5. PABP associates with poly-A tail and determines its length
30
Q

What are the three differences in protein synthesis between prokaryotes and eukaryotes?

A

Prokaryotes lack post-transcriptional modifications/processing
Only one RNA pol
No histones or nucleosomes

31
Q

What is hnRNA?

A

This is the immature mRNA

It still has introns

32
Q

What are the three main processes that occur in post-transcriptional modification?

A

5’ capping
Poly a tail
Splicing

33
Q

Describe the process of 5’ capping

A
  1. After 20-30 nucleotides, guanyl-transferase adds 7methyl guanosine to the end of the transcript
34
Q

Which enzyme adds the 5’ cap?

A

Guanyl transferase

35
Q

When does G-capping occur?

A

After 20-30 nucleotides have been synthesised in the mRNA transcript

36
Q

What is the function of the 5’ cap?

A

Orientation on the ribosome

Prevent degradation

37
Q

What is the structure of the poly-A tail?

A

Many adenine nucleotides added

38
Q

Which enzyme synthesises the poly-A tail?

A

PAP

Poly adenine polymerase

39
Q

What are consensus sequences and in what process are they important?

A

These are specific sequences of nucleotides in an mRNA transcript
These sequences are recognised by spliceosomes
The spliceosome recognises that region as an intron and then cuts it out

40
Q

What is the structure of a spliceosome?

Thus, it is …

A

snRNA And protein

Ribonucleoprotein

41
Q

What is the RNA in a spliceosome called?

A

snRNA

42
Q

What is snRNP?

What does it do?

A

Small nuclear RNA + protein
Ribonucleoprotein
It recognises the consensus sequences in introns so that they can be cut out

43
Q

What is the structure of ribosomes?

Thus it is a …

A

rRNA and protein

Ribonucleoprotein

44
Q

List some structures that are ribonucleoproteins

A
  1. Spliceosome, snRNPs
  2. Ribosome
  3. Telomerase
45
Q

What are the two subunits of the ribosome?

A

40S and 60S

46
Q

What are eIF?

A

Elongation initiation factors

These are required for addition of nucleotides to the mRNA transcript by the RNA pol
It moderates RNApol’s action
and rmoves histones

47
Q

Describe initiation of translation

A

eIF bring together the 7mG of 5’ cap, the 40S subunit of ribosome and MET tRNA

48
Q

When does the 60S subunit bind?

A

Wen the start codon is reached in the 40S subunit

49
Q

Describe the steps in translation elongation

A
  1. Empty A site
  2. Complimentary tRNA codon enters a site
  3. Bond forms between the amino acids in the A and P sites
  4. 60s shifts along
  5. tRNA in the E site is expelled, 40S moves along
50
Q

Describe the process of termination of translation

A

When the stop codon is in the a site, instead of a tRNA coming in, a termination factor comes in instead.
This causes the two subunits to dissociate

51
Q

What is the protein component of a spliceosome for?

A

The protein part of the spliceosome actually breaks the phosphorite steer bonds between nucleotides

52
Q

What is the other name for a spliceosome?

A

snRNP or SNURP

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