Microbiology Flashcards
What is an operon and it advantages?
A cluster of genes that are transcribed as a single messenger RNA
Advantage - many genes turned off at the same time
What is a repressor protein?
A regulatory protein that binds to specific sites on DNA INVOLVED IN NEGATIVE CONTROL
What is a helix turn helix motif? and how are they used in DNA binding sited
2 segments of a polypeptide chain linked by a three amino acid residue
Explain how the lac operon works in the presence and absence of lactose
No lactose: Lac genes aren’t needed – repressed by lac repressor – DNA polymerase is unable to bind to the promoter and no transcription occurs
Lactose: When lactose is present allolactose (inducer) is also present – binds to lac repressor protein so the repressor protein can’t bind to the operator — RNA polymerase binds to the promotor and transcription occurs
