lecture 7 recap

Question 1

eukaryotic mRNA components:

Answer 1

start codon (AUG) and stop codon
m7G cap at 5’ end
polyA tail at 3’ end

Question 2

why arent the m7G cap and polyA tail transcribed

Answer 2

because they are added after transcription

Question 3

the unfinished mRNA is known as

Answer 3

pre-mRNA

Question 4

what are the 4 events that occur to the pre-mRNA

Answer 4

capping
splicing
polyadenylation
editing

Question 5

CTD on the RNA pol II recruits required factors for these events making them coupled to

Answer 5

transcription

Question 6

capping:
RNA initially contains what at the 5’ end

Answer 6

triphosphate

Question 7

first step:
what is added onto the 5’ end

Answer 7

a G nucleotide

Question 8

the G then gets?

Answer 8

methylated

Question 9

functions of the m7G cap

Answer 9

1. protects mRNA from degradation by nucleases
2. facilitates splicing
3. facilitates export from the nucleus

Question 10

splicing:
exons are

Answer 10

coding sequences

Question 11

introns are

Answer 11

non coding sequences

Question 12

pre mRNA contains transcribed

Answer 12

introns and exons

Question 13

splicing is when

Answer 13

exons join together to get a continuous open reading frame

Question 14

intron and exon boundaries have conserved sequences called

Answer 14

5’ splice site
3’ splice site
branch site (in the middle)

Question 15

splicing reaction is

Answer 15

2 trans-esterification reactions

Question 16

step 1:
cut at 5’ SS and creat a bond between 5’ end of intron and

Answer 16

branch site

Question 17

step 2:
cut at 3’ splice site and release

Answer 17

intron lariat
introns are degraded and exons ligate together

Question 18

what is doing the splicing

Answer 18

the spliceosome (catalyses the removal of introns and ligation of exons)
requires ATP

Question 19

proteins in the spliceosome include

Answer 19

RNA binding proteins
ATPases
GTPases

Question 20

the complex contains snRNPS which are

Answer 20

small nuclear ribonucleoprotein particles

Question 21

snRNAs base pair with conserved sequences in the

Answer 21

intron

Question 22

snRNAs have an Sm binding site which is

Answer 22

(A/G)AUUUUUG(A/G)

Question 23

snRNAs pass through the middle of the

Answer 23

Sm protein structure

Question 24

snRNPs consist of

Answer 24

one of these snRNAs and the set of the Sm proteins

Question 25

people with systemic lupus erythematosus produce antibodies against the

Answer 25

Sm proteins

Question 26

firstly U1 binds to 5’SS then U2 binds to

Answer 26

the branch point

Question 27

the U4, 5 and 6 come in together and which is kicked out

Answer 27

U1 and U4

Question 28

U6, 2 and 5 carry out

Answer 28

step 1 and 2

Question 29

how does snRNA bind to the conserved sequences

Answer 29

by base pairing

Question 30

what is alternative splicing

Answer 30

means any exon can join to any other exon

Question 31

we have more different proteins in our cells than we have genes this is due to

Answer 31

alternative splicing

Question 32

polyadenylation is the

Answer 32

addition of polyA tail

Question 33

AAUAAA is a cleavage site for endonuclease from the RNA then you get addition of As by

Answer 33

polyA polymerase

Question 34

what does the polyA tail do

Answer 34

enhances export of RNA
stabilizes the 3’ end
enhances translation of mRNA