Genome Regulation: Gene Expression

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Questions and Answers

What is the primary function of gene expression in multicellular eukaryotes?

To regulate development and cell types (correct)

To control transcription factors

To respond to environmental changes

To produce enzymes through feedback inhibition

What is unique about eukaryotic gene regulation compared to prokaryotic gene regulation?

Operons are present in eukaryotes

Eukaryotes have a more complex regulation due to the presence of a nucleus (correct)

Eukaryotes respond quickly to environmental changes

Gene expression is faster in eukaryotes

What is the main reason why bacteria produce only the necessary products?

Natural selection has favored efficient bacteria (correct)

To regulate gene expression

To adapt to environmental changes

To conserve energy

What is the primary mechanism of gene expression regulation in bacteria?

Operon model Signup and view all the answers

What is the role of RNA molecules in eukaryotes?

To regulate gene expression Signup and view all the answers

What is the difference between short-term and long-term gene regulation in eukaryotes?

Short-term is for responses to environment, long-term is for development Signup and view all the answers

How do prokaryotes typically respond to environmental changes?

By regulating transcription factors Signup and view all the answers

What is the main difference between prokaryotic and eukaryotic gene expression?

Prokaryotes have operons, eukaryotes do not Signup and view all the answers

What is the term for a cluster of functionally related genes that are under coordinated control by a single 'on-off switch'?

Operon Signup and view all the answers

What binds to the operator and blocks RNA polymerase, preventing gene transcription?

Repressor Signup and view all the answers

What is the term for a molecule that cooperates with a repressor protein to switch an operon off?

Corepressor Signup and view all the answers

What is the name of the amino acid synthesized by E. coli?

Tryptophan Signup and view all the answers

What is the term for an operon that is usually on, but can be shut off by a repressor binding to the operator?

Repressible operon Signup and view all the answers

What is the term for an operon that is usually off, but can be turned on by an inducer inactivating the repressor?

Inducible operon Signup and view all the answers

What is the name of the operon that contains genes that code for enzymes used in the hydrolysis and metabolism of lactose?

Lac operon Signup and view all the answers

What is the molecule that inactivates the repressor to turn the lac operon on?

Inducer Signup and view all the answers

What type of pathways do inducible enzymes usually function in?

Catabolic pathways Signup and view all the answers

What is the term for the process of switching an operon off?

Repression Signup and view all the answers

Study Notes

Regulation of Gene Expression

Gene expression is altered in response to changing environments in both prokaryotes and eukaryotes.
In multicellular eukaryotes, gene expression regulates development and is responsible for differences in cell types.

Differences between Gene Expression in Prokaryotes and Eukaryotes

Prokaryote gene expression is typically regulated by an operon, a collection of controlling sites adjacent to polycistronic protein-coding sequences.
Eukaryotic genes are also regulated in units of protein-coding sequences and adjacent controlling sites, but operons are not known to occur.
Eukaryotic gene regulation is more complex due to the presence of a nucleus.

Types of Eukaryotic Gene Regulation

Short-term regulation: genes are quickly turned on or off in response to the environment and demands of the cell.
Long-term regulation: genes are involved in development and differentiation.

Operon Model

A cluster of functionally related genes can be under coordinated control by a single "on-off switch".
The regulatory "switch" is a segment of DNA called an operator, usually positioned within the promoter.
An operon is the entire stretch of DNA that includes the operator, the promoter, and the genes that they control.

Regulation of Operon

The operon can be switched off by a protein repressor.
The repressor prevents gene transcription by binding to the operator and blocking RNA polymerase.
The repressor is the product of a separate regulatory gene.
The repressor can be in an active or inactive form, depending on the presence of other molecules.

trp Operon

The trp operon is responsible for the synthesis of the amino acid tryptophan.
The operon is switched off when tryptophan is present, and switched on when tryptophan is absent.

Repressible and Inducible Operons

A repressible operon is one that is usually on; binding of a repressor to the operator shuts off transcription.
The trp operon is a repressible operon.
An inducible operon is one that is usually off; a molecule called an inducer inactivates the repressor and turns on transcription.
The lac operon is an inducible operon and contains genes that code for enzymes used in the hydrolysis and metabolism of lactose.

lac Operon

The lac operon is usually off, but is turned on when lactose is present.
The lac repressor is active and switches the lac operon off when lactose is absent.
Allolactose, an inducer, inactivates the repressor to turn the lac operon on.
Inducible enzymes usually function in catabolic pathways; their synthesis is induced by a chemical signal.

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Description

Quiz on regulation of gene expression in prokaryotes and eukaryotes, including its role in development and cellular differentiation.