Transcription in Prokaryotes Flashcards

Flashcards about transcription in prokaryotes, covering RNA types, RNA polymerases, transcription mechanisms, initiation, elongation, termination, regulation, and control elements.

What is the process of converting DNA instructions to RNA?

Transcription

Name three types of RNA molecules classified based on their function.

rRNA (ribosomal RNA), tRNA (transfer RNA), mRNA (messenger RNA)

What is the function of mRNA?

Acts as instructions for making proteins.

What metal ions are required by RNA polymerases?

Mn2+ or Mg2+

What are the 5 subunits that make up the catalytic core of RNA polymerase in E. coli?

α, α, β, β’, ω

What is the role of the sigma (σ) factor in transcription?

Used in transcription initiation; allows recognition of the promoter.

In what direction does RNA polymerase extend the RNA chain?

5’ to 3’

What are the two sequence elements that make up the promoter in prokaryotes?

-10 site (Pribnow box, TATAAT) and -35 site (TTGACA)

What is the function of the σ factor regarding the promoter?

Allows the enzyme to bind preferentially to the promoter.

Approximately how many base pairs of the DNA double helix does RNA polymerase unwind during synthesis?

Approximately 17 bp

What are the two mechanisms for the termination of transcription in prokaryotes?

Protein-independent termination and Protein-dependent termination

How does protein-independent termination occur?

Special (palindromic) sequences in RNA form a hairpin followed by a string of Us, causing RNA to detach from DNA.

Which protein facilitates protein-dependent termination?

ρ protein

In the repressor-inducer mechanism, what enzyme breaks down lactose?

β-galactosidase

What happens to the repressor in the absence of lactose?

Repressor binds to the operator, thus blocking transcription of lac operon.

What happens to the repressor in the presence of lactose?

Allolactose (derivative of lactose) binds to the repressor, removing it from the operator.

What does low glucose lead to?

Production of cyclic AMP (cAMP).

What is an inducer?

A chemical compound that stimulates transcription of a gene.

What is an Operator?

DNA sequence recognized by the repressor.