Unit 6 Part 2 Powerpoint Flashcards
What is the genomic composition of retroviruses?
A single strand of RNA
Retroviruses are unique among viruses in their RNA-based genome.
What enzyme do retroviruses use to copy their RNA genome into DNA?
Reverse transcriptase
This enzyme is crucial for the replication process of retroviruses.
What happens to retroviral DNA after it is formed?
It will integrate into the host cell genome
This integration allows the virus to utilize the host’s cellular machinery.
What does the host cell synthesize after the integration of retroviral DNA?
Viral RNA and proteins
These components are necessary for producing new viral particles.
How do viral progeny assemble in the host cell?
They assemble from synthesized viral RNA and proteins
This assembly process is essential for the propagation of the virus.
What do organisms often do in response to environmental change?
Regulate gene expression
This allows organisms to adapt to varying conditions.
What has natural selection favored in cells?
Cells that produce only the products needed
This efficiency is crucial for survival.
How can a cell regulate the activity of enzymes?
By feedback inhibition or enzyme production through gene regulation
These mechanisms ensure metabolic balance.
What model controls gene expression in bacteria?
The operon model
This model explains how genes are regulated in prokaryotic cells.
What is an operon?
The entire stretch of DNA that includes the operator, the promoter, and the genes that they control
Example: the Trp operon contains genes that code for tryptophan-synthesis enzymes.
What is the purpose of a regulatory ‘switch’ in gene expression?
To control a cluster of functionally related genes with a single ‘on-off switch’
The regulatory ‘switch’ is a segment of DNA called an operator usually positioned within the promoter.
Fill in the blank: A cluster of functionally related genes can be under coordinated control by a single _______.
on-off switch
What is the role of the operator in an operon?
It acts as the regulatory ‘switch’ for gene expression
The operator is usually positioned within the promoter.
True or False: The Trp operon is involved in the synthesis of tryptophan.
True
What is the function of an operator in an operon?
An operator is a binding site that permits or blocks transcription of the operon’s genes
Operators play a critical role in the regulation of gene expression.
What role do promoters play in transcription?
Promoters are binding sites (including the operator) that RNA polymerase and other transcription factors assemble on, initiating transcription
Promoters are crucial for the initiation of gene transcription.
What is the function of a repressor protein in an operon?
A repressor protein binds to the operator, blocking RNA polymerase from binding and stopping transcription
Repressors are key in regulating gene expression by preventing transcription.
What is the role of a corepressor in relation to a repressor?
A corepressor binds to the repressor, allosterically regulating it, locking it into its active conformation
Corepressors are essential for the activation of repressors, influencing transcription.
How does the corepressor affect transcription?
The corepressor’s activation of the repressor prevents transcription
This mechanism is part of negative regulation in gene expression.
What is the location and function of the regulatory gene in an operon?
The regulatory gene is upstream of the operon and codes for the repressor protein
The regulatory gene is crucial for the control of the operon’s transcriptional activity.
What is tryptophan?
An essential amino acid needed by E. coli for protein synthesis
Tryptophan is crucial for the functioning of E. coli.
What happens to the tryptophan operon under normal conditions?
It is usually ‘on’ and being transcribed
This indicates that the operon is actively producing proteins when tryptophan is available.
What type of operon is the tryptophan operon classified as?
Repressible operon
Repressible operons can be turned off under certain conditions, such as the presence of sufficient tryptophan.
