Regulation Of Transcription 1

Question 1

What does RNA world mean

Answer 1

Rna could self replicate and were catalytic to form proteins

Question 2

What is rnp world

Answer 2

Translation into proteins from rna

Rinonucleo proteins

Question 3

What is Luca

Answer 3

Last common ancestor that used DNA as genetic info store

Question 4

Is all rna translated

Answer 4

No but all rna modified

Question 5

What is the diff between euk and pro transcription and translation

Answer 5

Euk mrna needs to be exported to cytosol where ribosomes are

They are specially and time different

Question 6

What do viruses target

Answer 6

Regulation processes Eg txn regulation, export regulation or translation regulation

Question 7

Are 5’ m7g cap and poly a added post transcription

Answer 7

Yes. They aren’t encoded by genome

Question 8

Which 4 processes happen to form mrna from

Pre mrna

Answer 8

Capping splicing poly adenylation and editing

Question 9

What recruits factors for the 4 processes of mrna production Eg splicing

Answer 9

The CTD of rna pol II

Question 10

Which rnas are capped

Answer 10

All transcribed by rna pol II. Ie mrna, snrna and mirna

Question 11

How is a 5’ cap added

Answer 11

A guanosine with a ribose and guanine is added by 5’ phosphate attached to the ribose

The 5’ phosphate is the from the rntp terminally at 5’ which forms an unusual 5’ to 5’ between ribose then 3 P then another ribose at 5’ instead of 3’

The guanine N7 is then methylated (ch3) to form a cap

Question 12

How does the cap maintain mrna stability

Answer 12

It stops action of 5’ to 3’ exonucleases

Question 13

Proteins can bind via the methylation of guanosine at n7. What are they

Answer 13

Splicing factors
Export factors
Translation factors

Question 14

Give an example of an export factor that can bind to the m7g cap

Answer 14

Cbp80/20

Question 15

Which fsctor binds to cap in translation

Answer 15

Eif4

Question 16

What does splicing introduce in mrna

Answer 16

Open reading frames by removing introns

Question 17

Do most genes have introns

Answer 17

Yes but vary in size

Question 18

Which gene has largest introns

Answer 18

Dystrophin

Question 19

What are the 3 conserved sequences for intron and exon boundaries

Answer 19

5’ splice site
Branch site (A)
3’ oh splice site

Question 20

Which splice site has most pyrimidines Eg c or t (y)

Answer 20

3’ ss

Question 21

What does splicing reserved sequences recruit

Answer 21

Spliceosome

Question 22

How many reactions and what type is splicing

Answer 22

2 trans esterification reactions

Question 23

What is the first trans esterification reaction in splicing

Answer 23

5’ splice site is cleaved and joins the A branch site to form a lariat loop

Question 24

What happens in the second trans esterification reaction

Answer 24

3’ splice site is cut removing the lariat which is degraded

Ligation of the 2 exons occurs

Question 25

What is the spliceosome

Answer 25

Enzyme/ protein complex which gathers on each intron and uses atp

Question 26

What 4 things make up spliceosome

Answer 26

ATPase
Gtpase
Rna binding proteins (RBP)
Sn rnps (small nuclear ribonucleoproteins)

Question 27

What makes up snRNPs which are the catalytic unit of spliceosome

Answer 27

1 sm protein

1 sn rna (non coding)

Question 28

What sn rna in sn rnps base pairs with the 5’ splice site and cleaves it

Answer 28

U1

Question 29

Which sn rna base pairs with branch site Ain splicing

Answer 29

U2

Question 30

Which sequence is conserved in all sn rnas (u1,2,4,5,6)

Answer 30

Sm protein binding site

Question 31

Which autoimmune disease forms anti sm antibodies which react with the sm proteins in snRNPs

Answer 31

Lupus LSE

Question 32

Before the 2 step trans esterification what happens to pre mrna

Answer 32

U1 will bind to 5’ ss
U2 will bind to branch site

Forms A complex

Then u4,5,6 also bind onto the pre mrna

Forms b complex

Question 33

At what point does step 1 trans esterification occur

Answer 33

When u1 and u4 are released leaving only u2,5,6 (B* complex)

The lariat loops forms as 5’ ss is cleaved

Question 34

What complex are the sn rnas in when step 2 of trans esterification occurs

Answer 34

C complex u2,5,6

The 3’ ss is cut releasing the lariat with the sn rnas

The exons are ligated

Question 35

How can splicing form different protein isoforms from 1 gene

Answer 35

Alternative splicing

Question 36

Which 3 things can be mutated in splicing

Answer 36

The introns
The sn rnps (can’t slice efficiently)
Splicing factors

Question 37

Which sequence conserved during mrna transcription in 90% triggers poly adenylation

Answer 37

AAuAAA

Question 38

What region is found downstream of the poly A site

Answer 38

A g/U rich site

Question 39

What binds to the AAUAAA sequence and what does it bring to cleave the mrna to stop transcription

Answer 39

CPSF - cleavage and polyadenylation stimulating factor

Brings endonuclease

Question 40

What binds to the G/U rich downstream sequence after poly a site

Answer 40

CSTF - cleavage stimulatory factor

Question 41

What does CSTF cleavage stimulatory factor activate at the g/u rich downstream of poly A site

Answer 41

CF 1 and 2 (cleavage factor 1 and 2)

Question 42

Which enzyme allows encorporation of adenine residues at 3’ end

Answer 42

Poly a polymerase

Question 43

What 3 things does 250 poly A addition do via binding of proteins

Answer 43

Stabilise mrna from exonucleases (like cap)
Enhance translation (like cap does)
Allow exportation (like cap does)