3- Transcription

Question 1

What are the 3 rna polymerases

Answer 1

RNA Polymerase I -Transcribes rRNA genes
RNA Polymerase III- Transcribes tRNA and 5S RNA genes
RNA Polymerase II - Transcribes genes encoding proteins into mRNA

Question 2

Give 3 examples of functional rna

Answer 2

rRNA tRNA snRNA

Question 3

What is the gene promoter

Answer 3

The DNA sequence where the transcription complex assembles

Question 4

What does the basal transcription complex do

Answer 4

allows RNA polymerase II to be phosphorylated and then engage in transcription.

In the absence of binding of other Transcription Factors this produces a Basal (low) level of transcription.

It needs to be present for transcription to occur

Question 5

What is TATA

Answer 5

DNA sequence TATA is repeated to show RNA polymerase II where to bind
Upstream of this is the transcription factor binding site

Question 6

What is the 1st basal transcription protein to bind and what does it do

Answer 6

transcription factor II D (TF II D).
It contains TATA binding protein and TATA binding protein accessory factors.
On binding to the DNA molecule, it:
o Partially unwinds the DNA helix widening the minor groove to allow extensive contact with bases within the DNA
o This unwinding is asymmetric with respect to the TBP TATA complex, so transcription is unidirectional

Question 7

What order do the transcription factors bind in the basal transcription complex

Answer 7

TF ii D
TF ii A and B
RNA polymerase ii and TF ii F
TF ii H E J

Then other Transcription factors bind to the binding site and can interact with each other and the basal transcription complex to modulate transcription

Question 8

How do transcription factors facilitate transcription

Answer 8

By remodelling chromatin, by recruiting enzymes to modify histones (acetylation)

Question 9

Name some factors determining transcription factor expression

Answer 9

hormones, growth factors, mechanica stress, heat, cell contact, light, touch and voltage
Cell lineage
Mutation

Question 10

How does aspirin inhibit the inflammatory response

Answer 10

NFkB is a transcription factor which increases circulating cytokines. IkB inhibits this. Aspirin enhances this inhibition by preventing the breakdown of IkB prior to transcription. Hence NFkB is unable to enter the cell’s nucleus and transcription does not occur.