16 Questions
What is the consequence of abnormal gene expression in prokaryotes?
abnormal phenotype - cancer or cell death
In prokaryotes, at which level does the regulation of gene expression mostly take place?
transcription
What are inducible enzymes in the context of gene expression?
produced only when specific chemical substrates are present
Provide an example of a constitutive enzyme.
enzymes produced continuously, regardless of the chemical makeup of the environment
What is the effect of the presence of a specific molecule like tryptophan (trp) in the cell's environment?
it blocks the synthesis of enzymes necessary for tryptophan production
What triggers the synthesis of enzymes required for lactose metabolism in yeast?
When lactose is present in the growth medium
What is the difference between negative and positive control in gene expression?
Negative control shuts off gene expression by a regulatory molecule, while positive control turns on transcription only if a regulatory molecule directly stimulates RNA production.
Explain how lactose metabolism in E. coli is regulated.
Lactose metabolism in E. coli is regulated by an inducible system where gene expression is induced in the presence of lactose and repressed in its absence.
What is an operon and how is it related to gene regulation?
An operon is a group of genes regulated and expressed together as a unit. It is related to gene regulation as the entire gene cluster works as one system to respond to the presence or absence of specific molecules.
What are structural genes and regulator genes?
Structural genes code for proteins needed for the normal functioning of the cell, while regulator genes code for proteins that regulate other genes.
Describe the functions of the lacZ, lacY, and lacA genes in the lac operon.
The lacZ gene encodes b-galactosidase, which converts lactose to glucose and galactose; the lacY gene encodes permease, which facilitates the entry of lactose into the cell; the lacA gene codes for transacetylase, which removes toxic by-products of lactose metabolism.
Explain the concept of trans-acting and cis-acting regulatory regions.
Cis-acting regulatory regions bind to molecules that control transcription of the gene cluster, while trans-acting molecules bind to the cis-acting site and can regulate the expression of the gene cluster either negatively or positively.
What is the function of an inducer in gene regulation?
An inducer serves to turn on the expression of specific genes when present.
How does the transcription of the lac operon genes relate to the presence or absence of lactose?
The transcription of the lac operon genes is induced in the presence of lactose and repressed in its absence.
What are the differences between a repressible and an inducible system?
In a repressible system, gene expression is repressed by the presence of a specific molecule, while in an inducible system, gene expression is induced by the presence of a specific molecule.
Explain the concept of an operon being transcribed as a single unit.
An operon being transcribed as a single unit means that multiple genes within the operon are transcribed together into a single mRNA molecule.
Test your knowledge about the regulation of gene expression in prokaryotes, including transcription, translation, and metabolic responses to environmental changes. Explore how gene expression is controlled and the impact of abnormal gene expression on phenotypes such as cancer and cell death.
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