Lecture 15: Transcription

Question 1

What is the product of transcription?

Answer 1

RNA (not yet mRNA!)

Question 2

Where does transcription happen

Answer 2

INSIDE the nucleus

Question 3

Approximately how many base pairs are used to make RNA?

Answer 3

17

Question 4

What is RNA polymerase; what does it do and how many subunits does it have?

Answer 4

Synthesises RNA. Is a complex with 4 subunits

Question 5

Describe the pathway of RNA synthesis using RNA polymerase

Answer 5

DNA helix enters, small section of the strand is separated for RNA synthesis, rNTP comes in through another entrance, RNA is created, exits, and then the DNA exits too

Question 6

What does the PROMOTOR do?

Answer 6

Tells RNA polymerase where to begin

Question 7

How many types of polymerases do EUKARYOTES have? What do they do?

Answer 7

3.
Poly 1: transcribes genes that encode pre-ribosomal RNA
Poly 2: transcribes genes that encode tRNA; splicing
Poly 3: encodes ALL mRNA, genes, proteins

Question 8

What is the recognition sequence for RNA Poly 3?

Answer 8

TATA BOX

Question 9

What is the structure of RNA Poly 2 like?

Answer 9

12 subunits. Large and complex.

Question 10

What is the difference between GENERAL TRANSCRIPTION FACTORS and REGULATORY PROTEINS

Answer 10

General are required for the expression of almost all genes whereas regulatory proteins only regulate the expression of a subset of genes

Question 11

What proteins are requited for initiation of transcription of eukaryotes?

Answer 11

1. RNA Poly 2
2. TBP
3. TF2B
4. TF2H

Question 12

What is TBP? What does it do?

Answer 12

TATA-BINDING PROTEIN

Recognises the TATA box

Question 13

Describe the initation process in transcription

Answer 13

1. TATA box recognises the promotor region and beings. TATA protein binds
2. TF2B recruits poly 2 to bind to TBP
3. TF2H then also joins and unwinds the DNA

Question 14

What does TF2B do?

Answer 14

recruits poly 2 to bind to TBP

Question 15

What does TF2H do?

Answer 15

joins with TF2B and TBP, and unwinds the DNA,

Question 16

What is CTD? how does it interact with TF2H?

Answer 16

CTD is phosphorylated by TF2H which changes the conformation of poly 2 that allows it to begin elongation

Question 17

Where are the TATA box in the promotor sequences?

Answer 17

-30 region

Question 18

What do terminating factors do?

Answer 18

facilitate the dephosphorylation of CTD

Question 19

What three processes occur to make the RNA into mature mRNA?

Answer 19

• 5’ cap
• Poly A tail
• Splicing

Question 20

What does the 5’ cap do?

Answer 20

prevents mRNA from undergoing degradation, since it in unstable

Question 21

What does the spliceosome do?

Answer 21

Splices out INTRONS

Question 22

How is the Poly A tail added?

Answer 22

There is a sequence in the original gene that is transcribed onto mRNA as AAUAA….

Question 23

What happens during termination of transcription?

Answer 23

Phosphates are removed