MCB Lecture 20 Protein Synthesis Flashcards Preview

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Flashcards in MCB Lecture 20 Protein Synthesis Deck (53)
0

What is rRNA?

Ribosomal RNA that makes up the structure of ribosomes
Untranslated

1

What is mRNA?

Messenger RNA
Translated into proteins

2

What is tRNA?

Translational RNA
Delivers codons and amino acids
Untranslated

3

What is snRNA?

Small nuclear RNA
Makes up the spliceosome
Removes introns from hnRNA

4

Differentiate between RNAP in prokaryotes and eukaryotes.
What are the similarities and differences?

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

5

How do RNAP differ from DNApol?

They do not have proofreading mechanisms
Ey do not require primers

6

What is the function of RNA pol I?

Synthesised ribosomal RNA

7

What is the function of RNApol II?

Synthesised mRNA

8

What is the function of RNApol III ?

Synthesises tRNA

9

How do promoter regions differ in prokaryotes and eukaryotes?

There is much more variation in eukaryotic promoter regions

10

What makes up the transcription preinitiation complex?

RNApol
TFIID: TBP and TAF
And the other four GTFS

11

What are GTFs?
How many types are there?

General transcription factors
There are 5

12

What is TFIID comprised of?

TBP and TAF

13

What is TBP?

Where does it have a role?

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

14

What is TAF?

What does it do/associate with?

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

15

Describe the process of the preinitiation complex formation

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

16

Describe the function of the mediator

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

17

Describe the function of the activator

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

18

What do the Chromatin Modifying Proteins do?
Name one

SAGA is an example of chromatin modifying proteins

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

19

Describe how the enhancer, activator and mediator work together

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

20

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

TFIIH

21

What happens to the preinitiation complex when elongation starts?

The GTFs dissociate from the RNA Pol

22

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

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

23

Transcription elongation requires the recruitment of many other ...

eIF
Elongation initiation factors

24

What happens when specific termination sequences are transcribed?

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

What is CstF?

Cleavage stimulation factor

26

What is CPSF?

Cleavage and Polyadenylation Stimulating Factor

27

What is PAP

Poly adenylase polymerase

28

What is PABP?

Poly adenylase binding protein

29

How does the mRNA get cleaved from the RNAP?

What happens next?

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

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

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

31

What is hnRNA?

This is the immature mRNA
It still has introns

32

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

5' capping
Poly a tail
Splicing

33

Describe the process of 5' capping

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

34

Which enzyme adds the 5' cap?

Guanyl transferase

35

When does G-capping occur?

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

36

What is the function of the 5' cap?

Orientation on the ribosome
Prevent degradation

37

What is the structure of the poly-A tail?

Many adenine nucleotides added

38

Which enzyme synthesises the poly-A tail?

PAP
Poly adenine polymerase

39

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

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

What is the structure of a spliceosome?
Thus, it is ...

snRNA And protein
Ribonucleoprotein

41

What is the RNA in a spliceosome called?

snRNA

42

What is snRNP?
What does it do?

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

43

What is the structure of ribosomes?
Thus it is a ...

rRNA and protein
Ribonucleoprotein

44

List some structures that are ribonucleoproteins

1. Spliceosome, snRNPs
2. Ribosome
3. Telomerase

45

What are the two subunits of the ribosome?

40S and 60S

46

What are eIF?

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

Describe initiation of translation

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

48

When does the 60S subunit bind?

Wen the start codon is reached in the 40S subunit

49

Describe the steps in translation elongation

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

Describe the process of termination of translation

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

What is the protein component of a spliceosome for?

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

52

What is the other name for a spliceosome?

snRNP or SNURP

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