Transcription In Prokayotes

Question 1

Antisense strand?

Answer 1

Template strand, non coding strand

Question 2

RNA polymerase properties

Answer 2

1. No primer needed
2. 5’ to 3’ synthesis
3. Processive
4. Require DNA template

Question 3

RNA Polymerase structure

Answer 3

Core consisting of 2 alpha sub units, one beta and one beta prime subunit. Sigma holoenzyme. NB. Core is only capable of initiating transcription randomly. Sigma subunit identifies promoters and initiates transcription there

Question 4

Gene structure in prokaryotes

Answer 4

Promoter region
Coding sequence
Terminator region

Question 5

Sequence of -10 and -35 consensus box

Answer 5

-10 is TATAAT
Also known as TATA box

-35 is TTGACA

Question 6

Operon?

Answer 6

In genetics, anoperonis a functioning unit of DNA containing a cluster of genes under the control of a single promoter. .

Question 7

Pribnow box?

Answer 7

Also, -10 box. Located 5 to 10 bases upstream of transcription start site. Orients RNA polymerase as to the start and direction of synthesis.

Question 8

-35 sequence box

Answer 8

Initial site of subunit binding. Secind recognition site.

Question 9

Does RNA Polymerase have proofreading activity

Answer 9

No. In transcription, MANY copies are being made and they’re not very stable. Degraded right after coding for proteins. If there is a mistake it will make a non functional proteins, but there will be more functional than non functional proteins at the end of the day so no significant consequences arise

Question 10

How many mechanisms in termination in eukaryotes and what are they

Answer 10

2
Intrinsic termination involves a sequence within the elongating RNA which signals the RNA polymerase to stop. It forms a GC rich stem loop and a string of Us

Rho dependent factor uses a protein called rho factor to stop RNA synthesis at specific sites

Question 11

Rho dependent description?

Answer 11

So terminator is a sequence rich in C and Rho binds and poor in G. Rho binds to C rich sequence upstream of termination site. Moves along the RNA. Rho which is a helicase moves to the RNA polymerase location. Unwinds the DNA/RNA hybrid and RNA transcript is released. RNA polymerase and Rho dissociate

Question 12

Shine-Dalgano sequence. What is it

Answer 12

sequence upstream of coding region. Where ribosome binds

Question 13

Look at slide 30 before exam!

Answer 13

.

Question 14

Polycistronic gene regions

Answer 14

They are gene regions where a single promoter controls the transcription of multiple gene regions. But they each have their own shine dalgarno sequence, ie, ribsomoal binding site so their translation is done independently

Question 15

Topoisomerase II(Gyrase) relieves….and Topoisomerase I relieves….

Answer 15

Overwinding ahead of transcription bubble and underfunding behind bubble