Transcription II

Question 1

What’s the difference between prokaryotes and eukaryotes?

Answer 1

Non vs membrane bound nucleus

Question 2

RNA polymerase divides into I,II,III. Describe RNA polymerase I

Answer 2

Pre rRNA - Ribosome components, protein synthesis

Question 3

Describe RNA polymerase II

Answer 3

mRNA, snRNA, siRNA - All protein-coding genes, RNA splicing, repression, translation control

Question 4

Describe RNA polymerase III

Answer 4

Protein synthesis, Ribosome component, RNA splicing, insertion of peptides into ER

Question 5

Describe mRNA

Answer 5

Codes for proteins

Question 6

Describe rRNA

Answer 6

Form core of ribosomes structure, catalyse protein synthesis

Question 7

Describe (micro) miRNA

Answer 7

Regulate gene expression

Question 8

Describe tRNA

Answer 8

Adaptors between mRNA/AA during protein synthesis

Question 9

Describe other non-coding RNA

Answer 9

Used in RNA splicing, gene regulation, telomere maintenance

Question 10

Describe the role of transcription factor II (TFIIs)

Answer 10

Recognise the promoter (specifically for RNA polymerase II)

Question 11

Describe what RNA polymerase binds to

Answer 11

Binds and forms transcription initiation complex

Question 12

Describe the CAAT and GC box, including the TATA box

Answer 12

CAAT and GC box found in many promoters, but TATA box needed for initiation
(TATA found upstream)

Question 13

Describe the formation of the pre-initiation complex

Answer 13

TFs fall into place on DNA template with each one further stabilizing the preinitiation complex

Question 14

Describe the steps in Transcription - Initiation

Answer 14

1. Polymerase binds to promoter sequence in DNA (close complex)
2. Polymerase opens DNA near transcription start site forming bubble (open complex)
3. Polymerase catalyses phosphodiester linkage of 2 initial nucleotides
4. Polymerase moves 3’-5’ along template strand adding nucleotides to growing RNA (Rate of elongation - 1000 nuc/min at 37degs)
5. Transcription stop site, polymerase releases completed RNA and dissociates from DNA

Question 15

What does RNA polymerase II transcribe?

Answer 15

RNA poly II transcribes poly-adenylation sequence at end of gene (AAUAAA), then continues for 10-35 nuc, proteins recognise sequence, cut RNA free

Question 16

Describe how the transcription initiation is controlled

Answer 16

Using activators, Enhancers/Silencers, Coactivators, Repressors, Basal transcription factors

Question 17

Describe activators

Answer 17

Bind to genes on enhancers, speed up rate of transcription

Question 18

Describe enhancers/silencers

Answer 18

Affect efficiency of transcription, needed for initiation to occur

Question 19

Describe coactivators

Answer 19

Adapter molecules that integrate signals from activators/repressors

Question 20

Describe repressors

Answer 20

Bind to selected sets of genes and silencers, slowing transcription

Question 21

Describe basal transcription factors

Answer 21

Position RNA poly at start of transcription, initiate process

Question 22

Where is the CAP and Poly A tail found?

Describe the steps after these additions

Answer 22

5’ CAP and poly A at 3’ end
mRNA from degradation
Spliceosome removes introns to produce mature mRNA
Exons joined together

Question 23

What are the 2 functions of a cap?

Answer 23

Protects RNA from degradation

Needed for translation of mRNA

Question 24

What is the GU-AG rule?

Answer 24

Each intron cut at each end, almost always have GU at 5’/AG at 3’ end
Introns removed from primary transcript while RNA still being synthesised and after cap is added, but before transcript is transported into cytoplasm

Question 25

What are small nuclear ribonuclear proteins (snRNPS) / Snurps?

Answer 25

Eukaryotic intron in pre-mRNA molecule forms branched structure during RNA splicing, carried out by many RNA-protein complexes