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MCB*2050 > Lecture 2 > Flashcards

Lecture 2 Flashcards

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1
Q

What does Chromatin Condensation inactivate?

A

Gene Transcription

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2
Q

What type of eukaryotic DNA does transcription on?

A

One that is wrapped in chromatin

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3
Q

Why does chromatin need to be opened?

A

For a gene to be activated and transcription to proceed.

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4
Q

What is Chromatin Mediated Regulation often called?

A

Epigenetic Regulation of gene Expression

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5
Q

What is Heterochromatin?

A

Regions of chromosomes that are intensely stained

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6
Q

How is DNA packed in a heterochromatin?

A

Densely Packed

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7
Q

What is a Heterochromatin rich in?

A

Repetitive DNA (transposons, centromeres, and telomeres)

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8
Q

What is a heterochromatin not accessible to?

A

Transcriptional machinery

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9
Q

What is found in a heterochromatin?

A

Inactive genes

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10
Q

What is a Euchromatin?

A

Lightly stained chromosome regions

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11
Q

What is found in a Euchromatin?

A

Active Genes

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12
Q

What is a Euchromatin accessible to?

A

Transcriptional machinery

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13
Q

What happens once the gene is in open chromatin?

A

A very elaborate system and a variety of factors regulate the expression of each individual gene: far more complicated as compared to prokaryotes

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14
Q

What does RNA polymerase I synthesize?

A

Only pre-rRNA

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15
Q

What does RNA polymerase II synthesize?

A

mRNAs, some small nuclear RNAs (mRNA splicing), micro and small interfering RNAs that regulate translation and stability of mRNA’s

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16
Q

What does RNA polymerase III synthesize?

A

tRNA’s, 5S rRNA, and several other small stable RNAs

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17
Q

What is the RNA transcribed from from RNA polymerase I

A

Pre-rRNA (28S, 18S, 5.8S rRNAs)

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18
Q

What is the function of pre-rRNA?

A

Ribosome components, protein synthesis

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19
Q

What is mRNA transcribed by?

A

RNA polymerase II

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20
Q

What is the RNA function of mRNA

A

Encodes proteins

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21
Q

What is snRNAs transcribed by?

A

RNA polymerase II

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22
Q

What is the RNA function of snRNAs?

A

RNA splicing

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23
Q

What is siRNAs transcribed by?

A

RNA pol II

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24
Q

What is the RNA function of siRNAs?

A

Chromatin-mediated repression, translation control

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25
What is miRNAs transcribed by?
RNA pol II
26
What is the RNA function of miRNA's?
Translation Control
27
What is tRNAs transcribed by?
RNA pol III
28
What is the RNA function of tRNAs
Protein Synthesis
29
What is 5s rRNA transcribed by?
RNA pol III
30
What is the RNA function of 5s rRNA?
Ribosome component, protein synthesis
31
What is snRNA U6 transcribed by?
RNA pol III
32
What is the function of snRNA U6?
RNA splicing
33
What is 7S RNA transcribed by?
RNA pol III
34
What is the function of 7S RNA?
Signal recognition particle for insertion of polypeptides into the ER
35
What are other small stable RNAs transcribed by?
RNA pol III
36
What is the function of small stable RNAs?
Various functions
37
What is a characteristic of the crystal structure of the yeast RNA pol II?
Has been resolved at a High resolution (very active)
38
How many polypeptides does RNA pol II consist of?
12 polypeptides called RPB1, RPB2, etc..
39
What does all other eukaryotic RNA polymerases share?
Very high level of homology with the yeast RNA pol II
40
What does the Clamp Domain in the polymerase (RPB1) do?
Accommodate DNA.
41
After positioning over DNA what happens to the clamp?
It is closed by a bridge
42
Where does the synthesis of RNA take place in?
The catalytic centre with the participation of Mg++
43
Where does the synthesized RNA exit through?
A "channel" and is immediately capped by 7m Guanosine
44
What does Eukaryotic RNA polymerase II contain?
A unique Carboxy-Terminal Domain (CTD) of its RPB1 subunit
45
What is the Carboxy-Terminal Domain?
A specialized domain not found in any other polymerases, prokaryotic, or eukaryotic.
46
What is the CTD involved in?
Multiple regulatory interactions and plays a key role in initiation, elongation, and processing of mRNAs
47
What does the CTD in yeast contain?
26 repeats of Tyr- Ser - Pro - The - Ser- Pro - Ser
48
What does the CTD in mammals contain?
52 repeats
49
What happens to the Ser residue?
It gets phosphorylated during transcription from initiation to elongation
50
What is the structure like of the CTD?
Not structured (can't be seen under crystallography)
51
When is CTD of RNA Pol II phosphorylated?
During in vivo transcription
52
How is RNA Pol II genes regulated?
- Core Promoter Sequences* - Promoter-Proximal binding sites for activators - Distal Enhancers or Repressors - Chromatin Structure
53
What is the BRE?
- 37 to - 32 sites RNA Pol II TFIIB Recognition Element
54
What is the TATA Box?
- 32 to - 26 sites A Tight consensus sequence
55
What is the site of the Initiator
- 2 to +4
56
What is the site of the downstream promoter element?
+ 28 to +32
57
Where does transcription start?
At a defined point called the initiator site - Usually an A on the coding strand
58
What does BRE and DPE influence?
The activity of the promoter
59
What does DNA helicase help?
The polymerase initiate transcription.
60
What does Kinase help?
Release the polymerase
61
What are RNA Pol I General Txn. Factors labelled as?
TFIA and TFIB
62
What are RNA Pol II General Txn. Factors labelled as?
TFIIA, TFIIB, TFIID, TFIIE, TFIIH
63
What are RNA Pol III General Txn. Factors labelled as?
TFIIIB, TFIIIS

MCB*2050 (4 decks)

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