Transcription

Question 1

what is the central dogma made up of

Answer 1

DNA (storage and database), RNA (instructions), Proteins (products)

Question 2

what is transcription

Answer 2

making RNA from DNA

Question 3

what do RNA polymerases do

Answer 3

transcribe the template strand into a strand of RNA

Question 4

what determines where and when transcription occurs

Answer 4

promoters

Question 5

what is true of polycistronic bacterial mRNAs

Answer 5

they have a single promoter, contain multiple ribosome binding sites (RBS), usually contain genes in the same pathway or operon, code for multiple proteins

Question 6

what does RNA polyermase do

Answer 6

makes polymers of RNA using DNA as its guide

Question 7

what can RNA polymerase do that DNA polymerase cannot

Answer 7

it is capable of making dimers of the nucleic acid that it polymerizes

Question 8

how is RNA polyermase different from DNA polymerase

Answer 8

it does not need a primers, does not need a helicase, is less processive (does not go as far), has no proofreading ability

Question 9

why do bacterial RNAP require sigma subunits

Answer 9

allows the holoenzyme of RNAP to interact stably with DNA at the promoter

Question 10

what does sigma 70 do for RNAP

Answer 10

binds to the core enzyme of RNAP to create the holoenzyme which can then bind to DNA, find a promoter and create RNA

Question 11

what is the -35 sigma 70 promoter sequence on the coding strand / what is the -10 sigma 70 promoter sequence on the coding strand

Answer 11

TTGACA / TATAAT

Question 12

what do promoters do

Answer 12

they are a sequence of DNA that have several distinct regions that the RNA pol holoenzyme recognizes to start transcription

Question 13

what is the optimal distance between -35 and -10 sequences

Answer 13

16-18 bp - highly conserved

Question 14

what is the difference between a strong promoter and a weak promoter

Answer 14

strong promoters look more like the original sigma 70 sequence, weak promoters are not super identical to the original sigma 70 promoter sequence

Question 15

what are consensus sequences of promoters

Answer 15

they highlight the importance of each base in the sequence - how highly conserved it is across species

Question 16

how many parts does sigma 70 have / what do they do

Answer 16

it has 4 parts / they dramatically change what is expressed by the cell

Question 17

during the elongation phase of transcription can the RNA pol knock off other proteins bound to the DNA

Answer 17

yes it can - it the DNA-RNA complex is very stable (strong) and very fast

Question 18

why does RNAP not use proofreading

Answer 18

because so many RNAs are being made and a mistake in the RNA is not heritable so it really does not matter - proofreading also costs a lot of energy while slowing the polymerase down

Question 19

why can transcription occur at the same time as replication (if it is following)

Answer 19

there are periodic pauses during the transcription phase

Question 20

what is a terminator

Answer 20

a sequence at which RNA polymerase stops RNA synthesis

Question 21

what are the three steps of termination

Answer 21

1. the Core RNAP pauses 2. RNA-DNA duplex falls apart 3. RNA pol leaves DNA & releases RNA

Question 22

what are two types of termination

Answer 22

Rho-independent (intrinsic) and Rho-dependent

Question 23

what does intrinsic termination need

Answer 23

hairpin in RNA and a poly-U site (only RNA)

Question 24

what does rho-dependent termination require

Answer 24

rho protein, c-rich region

Question 25

where does translation of mRNA occur in bacteria / what does that mean for transcription and translation

Answer 25

in the cytosol / means transcription and translation can occur at the same time

Question 26

what does Rifampicin do / what is it used to treat

Answer 26

binds to the beta subinit - blocks the channel for mRNA to exit the RNAP / used to treat tuberculosis

Question 27

what does rifampicin not affect

Answer 27

does not affect already transcribing RNAPs