Gene Structure

Question 1

What does a prokaryotic genome look like

Answer 1

1. Circularized double stranded DNA
2. (Instead of wrapping around histones creating chromatin) circular structure forms a supercoiled structure with lots of loops
3. Many supercoiled structures attach to a protein core
4. DNA gyrase can help reduce supercoiling to allow replication and transcription

Question 2

What are enhancers roles in transcription

Answer 2

Provide structural support to bring proteins close to the RNA polymerase to make sure that it
binds to the promoter region, to initiate transcription

Question 3

What is the promoter region

Answer 3

1. Dictates where transcription starts and in which direction & which strand
2. This is the place that RNA polymerase binds to
3. Contains -10 and -35 consensus sequences
   (transcription start site (TATA box) and other sequences that recruit proteins able to assist in the control of initiation of transcription)

Question 4

What happens at the transcription start site

Answer 4

1. RNA polymerase and the DNA in the promoter region interact with one another.

The interaction depends on:
- Consensus sequence (a single base pair change in the -35 box can prevent binding).
- The shape of the DNA at the promoter and in the first ~50bp of the first gene.

Question 5

what are operons

Answer 5

1. Operons are structures where a number of genes are located next to one another on the genome
2. All genes get transcribed into one RNA strand known as a poly-cistronic RNA

Question 6

what does polycistronic mean

Answer 6

a single mRNA (generated from multiple genes) generates multiple protein