Transcription regulation in prokaryotes

Question 1

What is transcription?

Answer 1

The first and most regulated step of gene expression. A cell decides to switch on a gene by transcribing it. Once it does that, it will translate it and make it a protein.

Question 2

Example of defective transcription regulation in humans

Answer 2

Uncontrolled growth and division of cancer cells due to out-of-control transcription (due to, in turn, presence of mutant transcription factors).

Question 3

Example of rogue transcription in bacteria

Answer 3

Bacterium acquires a plasmid containing a gene encoding for an
antibiotic-resistance enzyme. Bacterium transcribes the gene,
translates the respective RNA and becomes antibiotic-resistant

Question 4

What are the steps of transcription?

Answer 4

1. Initiation (promoter binding and promoter melting by RNA polymerase)
2. Elongation (making of mRNA by RNAP)
3. Termination (dissocation of RNAP and mRNA from DNA)

Question 5

What way does transcription occur?

Answer 5

From the promoter to the terminator

Question 6

Initiation steps

Answer 6

• RNAP binds to the promoter in one orientation, with single base-pair precision!
• Promoter melts and the binding of the first complementary ribo-nucleotide occurs
• The promoter escapes and downstream movement of the enzyme begins