Molecular Micro Ch. 8 Regulation of Gene Expression I

Transcriptional regulation occurs at the level of what?

Initiation

What type of operon is characterized by a repressor protein normally being present until an inducer binds to it and causes a conformational change?

Negative inducible

What type of operon is characterized by a gene normally being freely transcribed and the repressor protein being inactive until bound by a corepressor, at which point it can bind and inhibit the operon?

Negative repressible

What is an example of a negative inducible operon?

lac operon

What is an example of a negative repressible operon?

trp operon

In the lac operon, what is lacI?

The gene for LacI repressor protein

In the lac operon, what is lacP?

The lac promoter

In the lac operon, what is lacO?

The lac operon

In the lac operon, what is lacZ?

The gene for beta-galactosidase

What is the purpose of the beta-galactosidase produced by the lac operon?

To break down lactose into glucose and galactose

In the lac operon, what is lacY?

The gene for a permease protein to let in more lactose

In the lac operon, what is lacA?

Gene for transacetylase enzyme

In the absence of lactose, what happens?

LacI binds to lacO and inhibits transcription from lacP

When lactose is present in small quantities in the cell, it can be metabolized to what?

Allolactose

What molecule (or inducer) binds to LacI, inducing a conformational change that makes it no longer able to bind to lacO?

Allolactose

What type of monomer is LacI?

Tetramer

What exact lacO sites does LacI bind to?

O1 and O3

What happens when LacI binds to O1 and O3?

It bends the DNA, making the promoter inaccessible

Of the two lacO sites, which is most important?

O1

Where is the O1 site located?

At the +1 site of the lac operon

In Blue-White screening, what type of sugar-agar is used to detect presence of beta-galactosidase?

X-gal

What is the name of the lac operon inducer used that is a non-metabolizable mimic of allolactose?

IPTG

From lecture, what was the use of marking LacI with a GFP fluorophore?

Visualize oriC and ter sites

What is tryptophan made from?

Chorismic acid

What is the name of the repressor protein in the trp operon?

TrpR

What type of repressor is TrpR?

Aporepressor

The TrpR aporepressor only becomes an active repressor protein after what corepressor binds to it?

Tryptophan

What type of negative regulatory systems govern catabolic and degradative operons?

Negative inducible

What type of negative regulatory systems govern biosynthetic pathways?

Negative repressible