Microbiology Final Exam

Microbiology Final Exam, A+ GURANTEED.

regulation of gene expression

–transcription initiation

–transcription elongation

–translation

2) alter activity of enzymes and proteins

–post translational

constructive genes-Answer housing keeping genes tha are expressed continuously by the cell

inducible genes-Answer –genes that code for inducible enzymes needed only in certain environments

–ex) beta galactosidase

inducible enzymes-Answer –functions in catabolic pathway

– present only when their sub state (inducer/effector molecule) is available

-beta galactosidase-Answer –inducible enzyme

–catalyzes lactose hydrolysis into glucose and galactose

repressible genes-Answer – enzymes that function in biosynthetic pathways are products of repressible
genes

–generally these enzymes are always present unless the end product in the biosynthetic pathway is
available

-regulatory proteins-Answer –repressor protein

–activator protein:

-repressor protein-Answer – negative control (decreases transcription)

–binds to operator

–interferes with binding of RNA pol to promoter or blocks movement of RNA pol after it binds

–inducer = substrate

– corepressor = enzymatic product

negative control of an inducible gene-Answer –negative: because there is a repressor

– inducible system because____

–repressor is bound to DNA on its own and blocks transcription; and induced activates repressor;
activated repressor no longer binds to DNA; transcription occurs

, – the repressor protein is active and prevents transcription when the substrate of the pathway is not
available

– inactivated by inducer

activated repressor is inactivated by inducer and causes (RNA pol can bind ––> increase toxin)

Negative control of a repressible system-Answer – negative control because it involves a repressor/ Apo
repressor

–Apo repressor is the repressor protein

– inactivated Apo repressor (without corepressor) does not bind to operator; ran pol does bind;
transcription occurs

–corepressor binds to Apo repressor activating it; repressor binds to operator; RNA pol can't bind; no
transcription

––inactive repressor (Apo repressor) is activated by corepressor and causes (RNA pol can't bind ––>
decrease toxin

Apo repressor-Answer –inactive repressor protein

– activated by corepressor

Activator proteins-Answer –positive control (increases toxin)

– binds to activator binding site

–promotes RNA pol binding to promoter

– Inactive activator protein is activated by inducer

–active activator protein is inactivated by inhibitor

Positive control of inducible gene-Answer – inactive activator is not bound to activator binding site and
ran pol cane bind and transcription is not occurring

–inactive activator is activated by inducer and the now active activator binds to activator binding site
and ran pol can now bind to promoter and tons increases

– Camp = inducer

–CAP = activator

Positive control of a repressible gene-Answer – active activator is bound to activator binding site and
RNA pol can bind to promoter and turning is occurring

–active activator is inactivated by inhibitor causing the inactivated activator to not bind to the activator
binding site and the RNA pol can no longer bind to promoter region and tan decreases

Lac operon-Answer CAP sight

Promoter