Bacterial Gene Regulation
What is the main purpose of transcription regulation in bacteria?
To control metabolism by turning genes on or off based on environmental conditions.
What is differential gene expression?
The process by which cells express different sets of genes, leading to cell specialization.
Why are viruses considered obligate intracellular parasites?
They cannot reproduce outside a host cell because they lack metabolic machinery.
What type of processes do inducible operons typically regulate?
Catabolic (breakdown) processes.
What is differential gene expression and why is it important?
It explains how cells with the same DNA (like neurons and muscle cells) can look and function differently by expressing different sets of genes.
What is an operon and why is it advantageous?
An operon is a cluster of genes under one promoter, allowing coordinated expression of related genes for efficiency.
How does DNA methylation affect transcription?
It condenses chromatin and reduces transcription by silencing genes.
Name one structural component of a virus.
Capsid, viral genome, or envelope.
Are inducible operons usually on or off? What turns them on?
They are usually off and turn on when the substrate is present.
How does chromatin structure influence gene expression?
Euchromatin is transcriptionally active (acetylated histones), while heterochromatin is inactive (methylated DNA and deacetylated histones).
In the trp operon, what role does the operator play?
The operator is a DNA segment where the repressor binds to block transcription.
What is the role of transcription factors?
They bind to promoters and enhancers to initiate or regulate transcription.
Why don’t antibiotics work on viruses?
Antibiotics target bacterial structures and processes, which viruses do not have.
What type of processes do repressible operons typically regulate?
Anabolic (biosynthetic) processes, like amino acid synthesis.
What is the role of transcription factors in gene regulation?
They bind to promoters and enhancers to recruit RNA polymerase and activate transcription; different cell types have unique transcription factors.
How do repressible and inducible operons differ?
Repressible operons (like trp) are usually on and turned off when product is abundant; inducible operons (like lac) are usually off and turned on when substrate is present.
Give an example of coordinate gene expression.
Hormone signaling, where multiple genes respond to the same transcription factor activated by a hormone.
Summarize the HIV replicative cycle.
HIV uses reverse transcriptase to convert RNA to DNA, integrates into host genome, and produces new viral particles.
Are repressible operons usually on or off? What turns them off?
They are usually on and turn off when the product is abundant.
Name two post-transcriptional mechanisms that regulate gene expression.
Alternative RNA splicing (produces different proteins from one gene) and mRNA stability (long-lived mRNAs make more protein).
Why do bacteria group genes into operons?
It allows simultaneous regulation of multiple genes involved in the same pathway, saving energy and resources.
What is alternative RNA splicing and why is it important?
It produces different proteins from the same gene, increasing protein diversity.
Why do RNA viruses mutate faster than DNA viruses?
RNA polymerases lack proofreading, leading to higher mutation rates.
Why is grouping genes into an operon advantageous for these pathways?
It allows coordinated regulation of all enzymes in the pathway using a single promoter, saving energy and resources.
What is the fastest and most reversible level of gene regulation, and how is Cyclin degraded during mitosis?
Post-translational regulation; Cyclin is tagged with ubiquitin and degraded by the proteasome.