Unit 3: Ch 15a Flashcards
what are the three types of gene expression?
- Constitutive – on all the time
- Inducible
- Repressible
what is a constitutive system of gene regulation in bacteria?
When some proteins are always produced, regardless of environment
what is are inducible systems of gene regulation in bacteria?
when bacteria acclimate to their environment by producing some proteins only when specific substrates are present
what is a repressible system of gene regulation in bacteria?
when there is an abundance of an end-product in the environment which represses gene expression
How is lactose metabolism in E. coli regulated by an inducible system?
because when lactose is available, the enzymes necessary to metabolize lactose are produced by genes
what is an operon?
a group of genes, all controlled by the same regulatory system
the lac operon consists of three regions, what are they?
lacZ, lacY, and lacA
the lac operon has an upstream _____ ______ consisting of an _____ and a _________
regulatory region, operator, and a promoter
lacZ encodes for _____, which is an enzyme that…
B(eta)-galactosidase, hydrolyzes the disaccharide lactose to the monosaccharides glucose and galactose
lacY encodes for _____, which is an enzyme that…
permease, facilitates the entry of lactose into the bacterial cell.
lacA encodes for ________, which is an enzyme that…
transacetylase, is involved in the removal of toxic by-products of lactose digestion from the cell.
where are regulatory regions located and are __-acting
they are located just upstream of the gene cluster and are cis-acting
what kind of proteins regulate the cis-acting sites?
trans-acting elements (grey pac man)
in the regulation of an inducible system, what is negative control?
its when a regulatory protein called a repressor binds to the operator and prevents RNA polymerase from binding properly to the promoter
in the regulation of an inducible system, what is positive control?
its when a regulatory protein, called an activator, binds to the operator and stabilizes RNA polymerase binding to the promoter
what happens when lactose is in the presence of the operon?
it binds to the repressor protein, causing repressor protein to change shape and chemical activity and transcription continues
what happens to when the I gene on an operon is mutated?
the repressor protein it produces cannot bind to the operator since the operator binding region of repressor is altered so transcription will happen and will always happen (constitutive)
what happens when the operator on an operon is mutated?
repressor protein cannot bind to the operator so transcription will always happen (constitutive)
what is an I^s mutation?
its a mutation where the I gene, which produces the repressor protein, cannot bind to lactose and so the repressor protein can always be bound to the operator which blocks transcription
In the absence of glucose and the presence of lactose, CAP exerts ________ by binding to the…
Positive Control, CAP-binding site and improving efficiency of RNA polymerase binding at the promoter region
