Prokaryotic transcription elongation

Question 1

Which direction is the RNA transcript synthesized?

Answer 1

5’ to 3’. Complementary to the template DNA

Question 2

What are the 2 reasons why DNA and RNAP are so stably associated during elongation?

Answer 2

1. RNAP is binding to dsDNA that is both entering and exiting the enzyme
2. The 8-9 bp RNA:DNA hybrid inside the enzyme that is complementary base pairing

Question 3

How does the RNA transcript leave RNAP?

Answer 3

A flap under the beta subunit, at the -14 nucleotide

Question 4

What is the +1 nucleotide during elongation?

Answer 4

The position that is in the RNAP active site, where the next nucleotide will be added

Question 5

How long does downstream DNA stay double stranded for?

Answer 5

Until it hits the +1 position. Only one base pair is unwound at a time

Question 6

Is the rate of transcription completely uniform?

Answer 6

No, certain sequences in the DNA or RNA transcript can cause RNAP to pause, stop entirely, or terminate transcription

Question 7

Why is it good for RNAP to pause at certain sequences?

Answer 7

Helps with proofreading, DNA repair, and can be a point of gene regulation. It also lets translation catch up to transcription