Lecture 33/34/35 Genetic Control Flashcards
Why do bacterial cells need to regulate the expression of their genes?
enzymes are energetically expensive; most efficient when they adapt to their environment
Constitutive
always on, always needed, essential
Posttranslational control
control of enzyme activity; no product (ex. inhibited active site)
Translational control
translational control; no protein synthesis (folded into a different shape)
Transcriptional control
transcriptional control; no mRNA synthesis; most efficient (control at level of the DNA)
Operon
one gene cluster transcribed as a single unit and is controlled by the same elements
An operon functions at which level of genetic control?
transcriptional control
What are the three components of an operon?
promoter, operator, structural genes
What are most regulatory proteins?
DNA binding proteins
What do inverted repeats do?
bind strongly to regulatory molecules
Allosteric protin
protein which has an catalytic (active) site and regulatory (allosteric/effector) site
What are the two types of allosteric proteins?
repressor proteins and activator proteins
Repressor proteins
proteins that bind to the operator site; stop RNA polymerase binding and turn OFF transcription
Activator proteins
proteins that bind to the activator site (upstream of operon); increase RNA polymerase binding and turn ON transcription
Types of Effector Molecules
1) inducers
2) activators
3) corepressors
Inducers
molecules that bind to repressors and result in transcription being turned ON (during neg. induction)
Activators
molecules that bind to activator proteins and result in transcription being turned ON (during pos. control)