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BIO EXAM 3 INFO > CHAP 8 > Flashcards

CHAP 8 Flashcards

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1
Q

What are the steps in transcription?

A

1) Initiation

2) Elongation

3)Termination

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2
Q

What occurs in initiation?

A

Binding of polymerase and opening of the DNA duplex

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3
Q

What occurs in elongation?

A

5’—>3’
nucleotides added at the 3’ OH end

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4
Q

How does transcription happen in prokaryotes?

A

RNA polymerase synthesizes RNA from DNA template
DNA-dependent RNA Polymerase
Holoenzyme

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5
Q

How many DNA-dependant RNA polymerases do prokaryotes have in transcription?

A

Only one

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6
Q

Describe the holoenzyme

A

6 polypeptides
core enzyme + sigma factor

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7
Q

Describe the sigma factor

A

Directs RNA pol the promoter and orients it properly
Dissociates from RNA pol after transcription begins

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8
Q

How many sigma factors are there?

A

7 of them

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9
Q

What are the informal (coding) RNAs?

A

mRNA

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10
Q

What are the functional (non-coding) RNAs?

A

tRNA
rRNA
snRNA
siRNA
miRNA

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11
Q

Describe tRNA

A

Transfer RNA

Key role in protein synthesis

Adaptor between mRNA and growing chain of amino acids

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12
Q

Describe rRNA

A

Ribosomal RNA

Makes peptide bonds

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13
Q

Describe snRNA

A

Small nuclear RNA

Components of spliceosomes

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14
Q

Describe siRNA

A

Small interfering RNA

Helps prevent infections

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15
Q

Describe miRNA

A

Micro RNA

Control of gene expression

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16
Q

Which type of RNA is most abundant?

A

rRNA (80% of RNA in cell)

17
Q

RNA is more _____ but less ____ than DNA

A

Flexible, stable

18
Q

Describe prokaryotes

A

No nucleus

Transcription and translation occur simultaneously

No post-transcriptional processing

Transcripts are polycistronic

19
Q

Describe polycistronic

A

When you make a mRNA transcript, many genes can be transcribed

20
Q

Describe transcription in eukaryotes

A

Initiation –> Elongation–>Termination

Three RNA polymerases

Transcription factors

21
Q

What are the three RNA polymerases and their functions

A

RNA Pol.I –> rRNA genes

RNA Pol.II–> A protein-coding genes (mRNA)

RNA Pol.III–> other small RNA genes (tRNA and 5S rRNA genes)

22
Q

Describe the transcription factors in eukaryotes

A

General transcription factors (GTFs) recruit RNA pol II to the promoter
Gene-specific transcription factors regulate RNA pol. II activity (activators and repressors)

23
Q

Describe CTD Phosphation

A

It is chemically modified to serve as a binding site for other proteins involved in transcription and RNA processing

Has a hydroxyl group that can be phosphorylated

24
Q

Describe capping

A

Occurs immediately after transcription initiation

C-terminal domain at the exit site

protect the 5’ end from the enucleation

Important for translation

25
Q

Describe splicing

A

Removes introns for primary transcript

involves spliceosomes

complex of snRNPs

Occurs in nucleolus, happens alongside transcription

26
Q

What are the snRNPs involved in splicing?

A

U1, U2, U4, U5, and U6

27
Q

What is the first GTF to bind to the promoter?

A

TFIID

28
Q

What does TFIIH do?

A

Melts away DNA/opens complex & does first set of phosphorylation

29
Q

What does TBP do?

A

Binds to the TATA box, it’s the TATA binding protein

30
Q

Describe the C-terminal domain

A

Helps bind different proteins

right by the exit site and is part of capping

31
Q

What does alternative splicing result in?

A

Production of related but distinct protein isoforms

32
Q

Describe polyadenylation

A

50-250 adenosine (A)

highly conserved (hexanucleotide) sequence AAUAAA

Protects the mRNA from decay and promotes translation by interacting with the translation machinery

33
Q

What is the 1/2 life of mRNA in eukaryotes?

A

20-30 minutes to 24 hours

34
Q

When does mRNA decay occur?

A

After the removal of the poly-A tail

Occurs in both directions

35
Q

Describe RNA interference

A

Inhibition of protein in synthesis from specific genes

involves either siRNAs or miRNAs

Results in the gene degradation of specific mRNAs

gene silencing

36
Q

Describe microRNA (miRNA)

A

Percent in genomes

Part of organism’s regulatory mechanism

regulates genomic gene expression

does NOT encode a protein

37
Q

Describe small interfering RNA (siRNA)

A

Present in genomes

shuts down unwanted foreign genetic elements such as viral RNA

organism’s defense mechanism

regulates genomic gene expression

does not encode a protein

38
Q

The template strand is the

A

non-coding strand, antisense strand

39
Q

The nontemplate strand is the

A

Coding strand, sense strand

BIO EXAM 3 INFO (3 decks)

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