L9 - transcription

Question 1

differences between DNA and RNA

Answer 1

1. DNA double stranded RNA single stranded
2. DNA has a H instead of OH on 2 carbon
3. RNA replaces T with U

Question 2

what type of RNA leaves nucleus to be translated

Answer 2

mRNA

Question 3

what is mRNA

Answer 3

copied from DNA in nucleus (transcription)

encodes protein

Question 4

what is rRNA

Answer 4

structural and enzymatic component of ribosome

Question 5

what is tRNA

Answer 5

delivers AAs to ribosome

Question 6

what type of polymerase is involved in transcription and translation?

Answer 6

RNA pol

Question 7

define transcription

Answer 7

production of mRNA from DNA

Question 8

what are the 3 steps of transcription (in prokaryotes)

Answer 8

initiation
elongation
termination

Question 9

what are the promoter sequences in prokaryotes and what position are they?

Answer 9

1. pribnow box (-10)

2. -35

Question 10

what are the functions of the promoter recognition sequences

Answer 10

align RNA pol to the transcription start site (via sigma factor)

Question 11

what do promoter recognition sequences often consist of and why?

Answer 11

T and A sequence

easier to separate

Question 12

function of sigma factor

Answer 12

recognises the -35 ad -10 promoter and binds them

then recruits the RNA pol in correct space

Question 13

why is sigma factor needed

Answer 13

RNA pol isnt specific so can bind to any region of DNA, sigma factor directs it to the transcription start site

Question 14

what unwinds the DNA during transcription?

Answer 14

RNA pol

Question 15

describe initiation

Answer 15

binding of sigma factor and RNA pol

Question 16

describe process of elongation

Answer 16

1. RNA pol unwinds DNA as it moves
2. RNA pol complimentary base pairs NTPs to template strand
3. sigma factor dissociates after first few nucleotides

Question 17

what provides energy for elongation process of transcription

Answer 17

PPi hydrolysis

Question 18

describe process of rho independent termination

Answer 18

1. mRNA transcript G-C rich stem loop sequence
2. reduces binding of mRNA to DNA and ‘pulls’ it away
3. after is a A-U rich sequence (easier to pull apart)

Question 19

describe process of rho dependant termination

Answer 19

1. rho protein follows behind DNA pol unwinding the newly synthesised RNA from the DNA strand
2. DNA pol pauses at certain sequences (eg G-C rich harder to unwind)
3. rho can catch up to DNA pol and terminate transcription

Question 20

what are the differences between prokaryote transcription and eukaryote transcription

Answer 20

1. eukaryotic has 3 RNA pols

Question 21

what does RNA pol 1 in E synthesise

Answer 21

rRNA

Question 22

describe structure of RNA pol 2

Answer 22

contains a C terminal domain tail

Question 23

what does RNA pol 2 in E synthesise

Answer 23

mRNA and snRNA

Question 24

what does RNA pol 3 in E synthesise

Answer 24

5s RNA and tRNA

Question 25

what is pre-mRNA/ hnRNA

Answer 25

the mRNA as soon as it has been transcribed | prior to processing

Question 26

what is the function of the CTD tail of DNA pol 2

Answer 26

co-transcriptional processing of pre-mRNA by : 1. capping 2. polyadenylation 3. splicing

Question 27

describe process of capping

Answer 27

7 methyl guanosine cap formed at 5' end of mRNA (looks like upside down nucleotide triphosphate)

Question 28

function of capping

Answer 28

protects end from degradation roles in export from nucleus roles in translation

Question 29

describe process of polyadenylation

Answer 29

enzyme adds multiple As to 3' end of mRNA | not encoded in DNA

Question 30

function of polyadenylation

Answer 30

protects end from degradation roles in export from nucleus roles in translation

Question 31

are exons or introns expressed

Answer 31

EXons | EXpressed

Question 32

what is splicing

Answer 32

removal of introns by splicosome

Question 33

what is alternative splicing

Answer 33

the process of splicing different combinations of exons as well as introns to give variation in protein products

Question 34

describe the sections of transcribed RNA

Answer 34

Tscription start--5'UTR--protein coding region--3' UTR