CHAP 8

Question 1

What are the steps in transcription?

Answer 1

1) Initiation

2) Elongation

3)Termination

Question 2

What occurs in initiation?

Answer 2

Binding of polymerase and opening of the DNA duplex

Question 3

What occurs in elongation?

Answer 3

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

Question 4

How does transcription happen in prokaryotes?

Answer 4

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

Question 5

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

Answer 5

Only one

Question 6

Describe the holoenzyme

Answer 6

6 polypeptides
core enzyme + sigma factor

Question 7

Describe the sigma factor

Answer 7

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

Question 8

How many sigma factors are there?

Answer 8

7 of them

Question 9

What are the informal (coding) RNAs?

Answer 9

mRNA

Question 10

What are the functional (non-coding) RNAs?

Answer 10

tRNA
rRNA
snRNA
siRNA
miRNA

Question 11

Describe tRNA

Answer 11

Transfer RNA

Key role in protein synthesis

Adaptor between mRNA and growing chain of amino acids

Question 12

Describe rRNA

Answer 12

Ribosomal RNA

Makes peptide bonds

Question 13

Describe snRNA

Answer 13

Small nuclear RNA

Components of spliceosomes

Question 14

Describe siRNA

Answer 14

Small interfering RNA

Helps prevent infections

Question 15

Describe miRNA

Answer 15

Micro RNA

Control of gene expression

Question 16

Which type of RNA is most abundant?

Answer 16

rRNA (80% of RNA in cell)

Question 17

RNA is more _____ but less ____ than DNA

Answer 17

Flexible, stable

Question 18

Describe prokaryotes

Answer 18

No nucleus

Transcription and translation occur simultaneously

No post-transcriptional processing

Transcripts are polycistronic

Question 19

Describe polycistronic

Answer 19

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

Question 20

Describe transcription in eukaryotes

Answer 20

Initiation –> Elongation–>Termination

Three RNA polymerases

Transcription factors

Question 21

What are the three RNA polymerases and their functions

Answer 21

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)

Question 22

Describe the transcription factors in eukaryotes

Answer 22

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

Question 23

Describe CTD Phosphation

Answer 23

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

Question 24

Describe capping

Answer 24

Occurs immediately after transcription initiation

C-terminal domain at the exit site

protect the 5’ end from the enucleation

Important for translation

Question 25

Describe splicing

Answer 25

Removes introns for primary transcript involves spliceosomes complex of snRNPs Occurs in nucleolus, happens alongside transcription

Question 26

What are the snRNPs involved in splicing?

Answer 26

U1, U2, U4, U5, and U6

Question 27

What is the first GTF to bind to the promoter?

Answer 27

TFIID

Question 28

What does TFIIH do?

Answer 28

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

Question 29

What does TBP do?

Answer 29

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

Question 30

Describe the C-terminal domain

Answer 30

Helps bind different proteins right by the exit site and is part of capping

Question 31

What does alternative splicing result in?

Answer 31

Production of related but distinct protein isoforms

Question 32

Describe polyadenylation

Answer 32

50-250 adenosine (A) highly conserved (hexanucleotide) sequence AAUAAA Protects the mRNA from decay and promotes translation by interacting with the translation machinery

Question 33

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

Answer 33

20-30 minutes to 24 hours

Question 34

When does mRNA decay occur?

Answer 34

After the removal of the poly-A tail Occurs in both directions

Question 35

Describe RNA interference

Answer 35

Inhibition of protein in synthesis from specific genes involves either siRNAs or miRNAs Results in the gene degradation of specific mRNAs gene silencing

Question 36

Describe microRNA (miRNA)

Answer 36

Percent in genomes Part of organism's regulatory mechanism regulates genomic gene expression does NOT encode a protein

Question 37

Describe small interfering RNA (siRNA)

Answer 37

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

Question 38

The template strand is the

Answer 38

non-coding strand, antisense strand

Question 39

The nontemplate strand is the

Answer 39

Coding strand, sense strand