In bacteria, gene expression is influenced primarily by WHAT?
Constitutive means what?
The gene is always on
Inducible means what?
Means that the gene is normally off, but it can be turned-on in response to a specific signal from the environment.
Repressible means what?
Means that the gene is normally on, but it can be turned-off in response to a signal from the environment.
If there is not sufficient glucose it its environment, E. coli can metabolize WHAT instead of glucose?
E.coli only expresses the genes for Lactose metabolizing enzymes (at high levels) when what?
Glucose is not available &
Lactose is present in the environment
What is an Operon?
In bacteria, a cluster of adjacent genes that share a common operator & promoter & are transcribed into a single mRNA. All the genes in an Operon are regulated coordinately; that is, all are transcribed or non are transcribed.
The structural genes that encode lactose metabolizing enzymes are organised into what?
What Lac gene encodes Beta-galactosidase?
What does Beta-galactosidase do?
Breaks down lactose
What Lac gene encodes Permease?
What does Permease do?
Transports lactose into the cell
What are the Structural Genes of the lac Operon?
lacZ, lacY, lacA
What comprises the Regulatory region?
Promoter & Operator
Transcription of the structural genes is controlled by what?
A WEAK promoter and an operator
What are the cis-elements of the lac Operon?
Promoter & Operator
What does it mean to be a cis element?
It means that in order to function the genes must be on the same DNA as the structural genes.
What is located nearby, but not a part of the Operon?
The regulatory gene lacI
What does the lacI gene encode?
What is the trans element of the lac Operon?
What does it mean to be a trans element?
This means that it functions just as well when lacI is on a different DNA molecule
Lactose metabolism in E. coli is regulated by what kind of system?
an Inducible System
The lactose genes are transcribed at a SIGNIFICANT level only when what is present?