Transcription

Question 1

what are the two basic featured of rna

Answer 1

• has ribose sugar (bears an OH group on its 2’ carbon)

- uracil in place of thymine

Question 2

describe coding region in a prokaryote

Answer 2

the coding region of a gene is often a single, continuous unit

Question 3

when does transcription and translation occur in prokaryotes

Answer 3

transcription and translation occur at the same time (are coupled)

Question 4

where does transcription occur in eukaryotes

Answer 4

in the nucleus

Question 5

where does translation occur in eukaryotes

Answer 5

in the cytoplasm

Question 6

describe the coding region of eukaryotes

Answer 6

the coding region in eukaryotes is often interrupted

Question 7

why is the coding region of eukaryotes often interrupted

Answer 7

• exons: protein coding segments

- introns: non-coding segments

Question 8

explain why transcription and translation are not coupled in eukaryotes

Answer 8

transcripts are made and processed in the nucleus and must be transported to the cytoplasm for translation

Question 9

what is the function of messenger rna

Answer 9

intermediates that carry genetic information from dna to the ribosomes

Question 10

what is the function of transfer rna

Answer 10

adapters between amino acids and the codons in mrna

Question 11

what is the function of ribosomal rna

Answer 11

structural and catalytic components of ribosomes

Question 12

what is the function of small nuclear rna

Answer 12

spliceosomes and rRNA & tRNA modification

Question 13

what is the function of micro rna

Answer 13

shirt rna that block expression of complementary mrna

Question 14

what are the three types of micro rna

Answer 14

miRNA, siRNA, crisprRNA

Question 15

what is the function of long-non-coding rna

Answer 15

long rna that regulate gene transcription

Question 16

which direction is rna synthesized in

Answer 16

rna is synthesized in the 5’ to 3’ direction using the 3’ to 5’ dna strand

Question 17

what is the chemical reaction of transcription

Answer 17

RNA+rNTP=RNA +PP1

Question 18

what’s the precursors to rna synthesis

Answer 18

ribonucleoside triphosphates

Question 19

how many strands of dna are used as a template in rna synthesis

Answer 19

only one strand of dna is used as a template

Question 20

do rna chains need a primer

Answer 20

rna chains can be initiated without a primer

Question 21

what is rna synthesis catalyzed by

Answer 21

rna synthesis is catalyzed by rna polymerase and proceeds in the 5’ to 3’ direction

Question 22

what are the three steps in transcription

Answer 22

1. initiation
2. elongation
3. termination

Question 23

describe the initiation step in rna synthesis

Answer 23

rna polymerase binds, unwinds, and joins first 2 nucleotides
-does not require a primer

Question 24

describe the elongation step in rna synthesis

Answer 24

complementary nucleotides continue to be added during elongation
-localized dna unwinding ahead of rna polymerase generates a transcription bubble

Question 25

what is the function of the transcription bubble

Answer 25

moves with the rna polymerase and the unwound dna rewinds behind it

Question 26

describe the termination step in rna synthesis

Answer 26

transcription stops when rna polymerase reaches the "terminator" region of the gene

Question 27

what happens when termination occurs

Answer 27

rna and rna polymerase are released

Question 28

what is the function of the core in e.coli rna polymerase

Answer 28

transcribes any dna

Question 29

function of holoenzymes in e.coli rna polymerase

Answer 29

transcribes specific genes

Question 30

function of the alpha holoenzyme in e.coli rna polymerase

Answer 30

assembly of the tetrameric core

Question 31

function of the beta holoenzyme in e.coli rna polymerase

Answer 31

ribonucleoside triphosphate binding site

Question 32

function of the beta' holoenzyme in e.colu rna polymerase

Answer 32

dna template binding region

Question 33

function of the W holoenzyme in e.coli

Answer 33

not essential for transcription but it stabilizes core

Question 34

describe what happens in initiation of transcription in e.coli

Answer 34

- promoter recognition requires the rna polymerase holoenzyme - sigma factor recognizes and binds to the -35 element

Question 35

what happens once the sigma factor recognizes and binds to the -35 element

Answer 35

once the sigma factor recognizes and binds to the -35 element, the rna polymerases is positioned at the promoter to begin transcription

Question 36

where does transcription initiate in e.coli

Answer 36

transcription initiates about 5-9 base pairs down from the end of the -10 sequence

Question 37

what is the -35 sequence

Answer 37

AACTGT

Question 38

what is the -10 sequence

Answer 38

ATaTTA

Question 39

when does transcription elongation in e.coli happen

Answer 39

occurs when sigma factor is released and rna polymerase begins to move along the 3' to 5' dna template strand

Question 40

describe termination in e.coli

Answer 40

-weak bonding of U:A residues allows mrna release form dna when rna polymerase pauses at terminator (release of transcript when rna polymerase pauses after hairpin formation)

Question 41

what are puffs in drosophila

Answer 41

puffs in drosophila chromosomes are sites of localized unwinding due to gene transcription

Question 42

how many polymerases do eukaryotes have

Answer 42

most eukaryotes have three rna polymerases

Question 43

what does rna polymerase 1 do

Answer 43

present in all eukaryotes, and transcribes large rna

Question 44

what does rna polymerase 2 do

Answer 44

present in all eukaryotes transcribes rna

Question 45

what does rna polymerase 3 do

Answer 45

present in all eukaryotes, transcribes rna

Question 46

hat does rna polymerase 4 do

Answer 46

present in plants, transcribes some siRNA

Question 47

what does rna polymerase 5 do

Answer 47

present in plants

Question 48

genes transcribed by which polymerases have specific promoters

Answer 48

there are specific promoters for genes transcribed by pol1,2,3

Question 49

what does initiation in eukaryotes involve

Answer 49

initiation in eukaryotic transcription involves step-wise assembly of general transcription factors

Question 50

what happens during basic initiation in eukaryotic transcription

Answer 50

-forms "preinitiation complex" which is sufficient to initiate transcription

Question 51

what happens during more complex initiation in eukaryotes

Answer 51

more complex transcriptional regulation involves a multi-subunit complex called "mediation"

Question 52

what is the multi-subunit complex mediation

Answer 52

mediation permits interaction with other activator proteins bound to upstream/downstream regulatory regions or enhancer sequences

Question 53

where are the transcriptional factors when the elongation step is reached in eukaryotes

Answer 53

at the elongation stage, many of the general transcription factors remain at the promotor providing for a quick re-initiation with a new polymerase

Question 54

as the general transcription factors remain at the promotor at the beginning of the elongation stage, what is the benefit?

Answer 54

as the general transcription factors remain at the promotor at the beginning of the elongation stage, this makes for a quick re-initiation with a new polymerase

Question 55

describe termination in eukaryotic transcription

Answer 55

-involves cleavage of pre-mrna and 5' to 3' degradation of the remaining rna by the RAT1 exonuclease