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Foundations 1 > Transcription > Flashcards

Transcription Flashcards

1
Q

What is the initiation site of transcription?

A

Promoter

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2
Q

What are the components of a transcription unit?

A

Promoter
Structural gene
Terminator
*Eukaryotes also have enhancers

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3
Q

What is the enzyme used in prokaryotes for transcription and its factors?

A

RNA polymerase
Sigma factor for initiation
Rho factor for termination
Contains two zinc molecules

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4
Q

In what direction is RNA synthesized

A

5’ to 3’

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5
Q

What does RNA pol lack compared to DNA pol?

A

Proofreading activity
Does not need primer

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6
Q

What is the promoter site in prokaryotes?

A

Upstream of start codon that contains consensus sequence
~35 nucleotides upstream is TTGACA
~10 nucleotides upstream is TATA box (Pribnow) TATAAT

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7
Q

What is released at beginning of elongation in prokaryotes?

A

Sigma factor

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8
Q

What are the two types of termination in prokaryotes?

A

Rho factor dependent
Rho factor independent

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9
Q

What is rho factor dependent termination?

A

Termination sequence recognized by rho factor
ATPase with helicase activity that disrupts RNA-DNA complex

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10
Q

What is rho factor independent termination?

A

Palindromic sequences - self-complementary
Creates hairpin structure that disrupts RNA pol
String of Us causes RNA to dissociate from DNA template
More common

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11
Q

What are some antibiotic inhibitors of prokaryotic transription?

A

Rifampin
Actinomycin

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12
Q

What are the 3 RNA pol in eukaryotes?

A

RNA pol I
RNA pol II
RNA pol III

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13
Q

What is the function of RNA pol I?

A

Synthesizes pre-rRNA 28S, 18S, 5.8S in nucleolus

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14
Q

What is the function of RNA pol II?

A

Synthesizes pre-mRNA in nucleus

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15
Q

What inhibits RNA pol II?

A

alpha-amanitin

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16
Q

What is the function of RNA pol III?

A

Synthesizes pre-tRNA in nucleus
Synthesizes pre-rRNA 5S in nucleolus
Synthesizes some snRNA and snoRNA

17
Q

What encodes transcription factors?

A

Trans-acting elements

18
Q

Where can TFs bind?

A

Core promotor site
Close to gene
Distal to gene

19
Q

What is the function of TFs?

A

Assembly of transcriptional complex at promoter
Determination of what genes are transcribed

20
Q

What are general TFs?

A

Required for all genes
Near start site - assembly of initiation complex
Recognize promoter, recruit RNA pol, and initiate transcription

21
Q

What are specific TFs and their functions?

A

Stimulate or repress particular genes
Transacting factors
Modulate frequency of initiation
Mediate response to signals
Bind to coactivators

22
Q

What are two examples of proximal regulatory elements?

A

CAAT box
GC box

23
Q

What are the events in initiation?

A

TFIID binding to TATA box
TFIIF recruits pol II to TFIID
TFIIH has helicase activity

24
Q

What is an exon?

A

Gene segment that codes for protein

25
Q

What is an intron?

A

Noncoding sequence the interrupts exons of a gene

26
Q

What is rRNA PTM?

A

RNAses remove introns and cleave into subunits
In nucleolus

27
Q

What is tRNA PTM?

A

Removal of introns
Base modification
CCA added to 3’ end
In nucleus

28
Q

What is mRNA PTM?

A

None in prokaryotes
Co and post in eukaryotes
5’ cap
Poly-A-tail to 3’ end
Removal of introns
Alternative splicing
In nucleus

29
Q

How does 5’ cap occur and what is its function?

A

Enzymes Guanyl transferase and Guanine methyl transferase

Stabilize mRNA
Ribosome binding site
Efficient translation

30
Q

What is poly-A-tail and its function?

A

Addition of 200-250 A residues in response to AAUAAAA signal by polyadenylate polymerase

Stabilizes mRNA
Facilitates exit from nucleus
Aids translation
Prevents degradation

31
Q

How does splicing occur?

A

snRNA form snRNP that mediate splicing

32
Q

What are p-bodies?

A

Processing bodies
Site of mRNA degradation and storage
Cytoplasmic RNP

Foundations 1 (28 decks)

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