Biochemistry - Transcription Flashcards

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1
Q

What are the two steps of protein synhesis?

A

Transcription
Trnaslation

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2
Q

RNA polymerase

A

This is the the primary gene expression enzyme transcribing DNA into RNA.

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3
Q

What does RNAP II do?

A

Primary eukaryotic polymerase for all protein-coding genes and non=protein RN like nuclear RNA.

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4
Q

What does RNAP III do?

A

Transcribes tRNA genes and the 5S component of rRNA.

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5
Q

What is gene regulation mediated by?

A

Promoters like enhancers and silencers.

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6
Q

Promoters

A

Regulatory regiosn where polymerases or TFs bind to initate gene transcription

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7
Q

What region do RNAP bind?

A

The TATA box of the promoter.

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8
Q

TATA box

A

This defines transcription direction and indicates the DNA strand to be read

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9
Q

How do enhancers and silencers work?

A

Bind the TATA box and regulate their activity.

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10
Q

What is required of the chromosome for transcription?

A

Chromatin remodelling complex opening of nucleosomes.

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11
Q

What are the five TF mediating RNAPII function?

A

TFFIIB, E, D, F and H

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12
Q

Why does so much cell variety exist in organisms?

A

Due to the variability by gene regulatory networks like enhancers and silencers.

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13
Q

Gene Regulatory Networks

A

Molecular regulators interacting with TFs and genes to regulate mRNA expression

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14
Q

Enhancers

A

Amplify gene expression, can be up to 1 million base pairs away, but on average 100-1000 bp.

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15
Q

Intergenic

A

In between active genes

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16
Q

Intronic

A

In between exons, on the introns.

17
Q

Where are enhancers, super-enhancers and silencers found?

A

Intergenic and intronic regions

18
Q

What happens in initaiton of PS?

A

TBP brings promoter DNA into contact with TFIIB of RNAPii, destabilising DNA to prepare elongation.

19
Q

What happens when RNAPII first contacts promoter region?

A

It folllows until 25-30bp from TATA, where transcription site near polymerase active site, where TFIIE and H is recruited.

20
Q

TFIIH

A

Destabilises DNA duplex to allow thermal unwinding forming transcription bubble.

21
Q

Transcription bubble

A

A complex formed when a limited portion of the DNA double helix is unwound.

22
Q

Template Strand

A

The strand copied to synthesise mRNA

23
Q

What happens after TFIIH destabilises DNA?

A

TFIIF binds non-template strand, whilst template strand follows through polymerase active site three NT deep, bending sharply and then clamped for elongation

24
Q

Elongation

A

This is the successive transcription of nucleotdies of the template strand from 5’s to 3’

25
Q

Which end are nucleotides transcribed from?

A

3’ end.

26
Q

How does trigger loop permit hydrogen bond formation in the polymerase?

A

Trigger loop containing histidine residue alternates between clamping sites, promoting electron flow coupled with phosphodiester bond formation.

27
Q

What are the two trigger loop states?

A

One allows NTP to enter active centre, and a closed state holding NTP in the active centre

28
Q

When during PS can a second roundo of transcription occur?

A

After about 50-60NT are expressed.

29
Q

What are the processesing pathways primary transcript undergoes after formation?

A

7’methylguanosie cap addition
3’ polyadenylation
Splicing of introns

30
Q

Why is 7’MG cap addition important?

A

It allows ribosomal recognition for syntheses?

31
Q

What happens in 3’ adenylation?

A

The 3’ undergoes exonuclease digestion to a short sequence where a poly-a tail can be added.

32
Q

Why is it important transcription and RNA processing are coupled?

A

The occurence of one regulates the next, limiting diffusion required for progression.