Lecture 9: Control of Gene Expression

What is the main goal of prokaryotic reproduction?

Reproductive efficiency, not fine-tuning.

What is cell differentiation?

The regulation of the roles of cells at different stages of development.

What does natural selection prioritize in bacteria?

Bacteria that produce products necessary for survival and reproduction.

What is feedback inhibition?

A method that regulates enzyme activity by cutting off the first enzyme in a metabolic pathway.

What is an operon?

A cluster of functionally related genes under control of a single 'on/off' switch.

What is a repressor protein?

A protein that can switch repressible operons 'on/off'.

What characterizes repressible operons?

They are usually active and require a corepressor to repress the pathway.

What characterizes inducible operons?

They are normally off and require an inducer to switch on.

What is the difference between inducible and repressible operons?

Inducible operons are off by default and activated by an inducer; repressible operons are on by default and turned off by a repressor.

What is CAP in the context of positive gene regulation?

Catabolic activator protein that helps RNA Polymerase promote transcription when glucose is low.

What is the function of sigma factors?

They help RNA Polymerase recognize the promoter to initiate transcription.

What are euchromatin and heterochromatin?

Euchromatin is loosely packed and favorable for gene expression; heterochromatin is tightly packed and less accessible for transcription.

What role do histone modifications play?

They affect the packing density of chromatin and subsequently gene expression.

What is DNA methylation?

The addition of a methyl group to inhibit transcription of specific DNA sequences.

What are control elements?

Noncoding portions of DNA that regulate transcription.

What is the Poly-A Signal Sequence?

A sequence that adds a poly-A tail to mRNA and signals the end of transcription.

What is the role of general transcription factors?

They are required for transcription and help recruit RNA Polymerase.

What is a repressor?

A protein that inhibits the expression of specific genes.

Why is coordinated control important?

It ensures the correct combination of activators is present to express the necessary proteins.

What does FISH stand for?

Fluorescence in situ hybridization, a technique to identify specific mRNAs.

What is mRNA processing?

The modification of pre-mRNA to mature mRNA by splicing and adding 5' and 3' caps.

What is RNA interference (RNAi)?

The inhibition of gene expression by noncoding RNA molecules.

What are microRNAs (miRNAs)?

Noncoding RNAs that regulate gene expression by degrading complementary mRNA.

What is the function of proteasomes?

Giant protein complexes that degrade damaged or unneeded proteins.

What is morphogenesis?

The physical process that provides an organism its shape.

What are cytoplasmic determinants?

Maternal substances in the egg that influence early development.

What is induction in embryonic development?

The process by which signal molecules cause transcriptional changes in nearby target cells.

What are oncogenes?

Cancer-causing genes that originate from normal proto-oncogenes.

What is the role of tumor-suppressor genes?

To prevent uncontrolled cell growth by repairing DNA, controlling cell division, inhibiting the cell cycle, and promoting apoptosis.

What are enhancers?

Distant control elements that regulate transcription and can be located far from the gene they control.

What is the role of RNA Inducing Silencing Complex (RISC)?

It binds to miRNAs and degrades complementary mRNA.

What occurs if the Dicer enzyme is removed?

miRNA hairpin structures fail to form single strands, leading to developmental issues.

What do active repressors do?

They inhibit transcription through protein-protein interactions.

What is the significance of mRNA's untranslated regions (UTRs)?

They can contain regions that activate or inhibit proteins.

What does splice out mean in the context of mRNA processing?

To remove introns from the pre-mRNA molecule.

What happens to mRNA lifespan in the cytoplasm?

It determines how long a protein can be synthesized.

What is gene expression regulation?

The ability of cells to control which genes are expressed at any given time.

What is histone acetylation?

A modification that loosens chromatin structure and promotes transcription.

What are regulatory transcription factors?

Proteins that interact with specific control elements to enhance or inhibit transcription.

What is the typical outcome of double-stranded RNA in the context of viruses?

It is targeted for degradation by siRNAs.

What does the term 'noncoding RNA' refer to?

RNA molecules that do not code for proteins but can have regulatory functions.

What is the function of the promoter in gene expression?

It is the DNA sequence where RNA Polymerase binds to initiate transcription.

How does glucose affect the activity of CAP?

When glucose levels rise, CAP releases from cAMP, decreasing activation of transcription.

What is the role of chromatin remodeling in gene expression?

It alters chromatin structure to make genes either accessible or inaccessible for transcription.

What determines the specific proteins that will be expressed in different cells?

The combination of regulatory transcription factors present.

What is the purpose of adding caps to the mRNA?

To protect it from degradation and assist in the export from the nucleus.

What happens to an operon when a corepressor binds to a repressor?

The repressor becomes active and binds to the operator to inhibit transcription.

What might be affected if RNAi is inhibited?

Gene expression regulation would be disrupted, leading to overexpression of mRNA.

What is the significance of the morphogen gradient?

It helps establish an embryo's axis of growth.

What does a transcription factor's 'activator' domain do?

It binds to DNA and initiates transcription by facilitating protein interactions.

What type of genes are proto-oncogenes before mutation?

Normal genes regulating cell growth and differentiation.

What is a signal for histone methylation?

It signals to densify chromatin and inhibit transcription.

What does 'epigenetic factors' refer to?

Modifications to DNA and histones that affect gene expression without changing the DNA sequence.

How do stem cells differ from specialized cells?

Stem cells have the potential to become multiple cell types depending on developmental needs.

What is a corepressor?

A small molecule that binds to a repressor protein and activates it.

What is the function of nuclear architecture in gene expression?

It may position chromosomes in dense regions of transcription factors to regulate gene expression.

What occurs during mRNA degradation?

The lifespan of mRNA in the cytoplasm is key to controlling protein synthesis.

How does the presence of siRNAs influence gene expression?”,

They can specifically target and degrade complementary mRNA molecules.

What is the purpose of adding a poly-A tail to mRNA?

It enhances stability and is involved in the termination of transcription.

Why is gene regulation crucial in multicellular organisms?

It allows for specialization of cells and proper development.

What happens to chromatin when histones undergo acetylation?

Chromatin structure loosens, making transcription more likely.

What is the outcome of transcriptional regulation?

It determines which genes are expressed and to what level.

What role do microRNAs (miRNAs) play in the gene regulatory network?

They are critical for post-transcriptional regulation of gene expression.

What are the implications of a mutation in a tumor-suppressor gene?

It can lead to uncontrolled cell growth and cancer.

What type of genes do morphogens influence?

Transcription factors that affect morphogenesis and development.

Why is it important for RNA Polymerase to bind to the promoter?

It initiates the transcription of the gene into mRNA.

What happens to mRNA after it is translated?

It may be degraded, influencing how long the protein is available.

What do splicing enzymes do?

They remove introns and join exons in the processing of pre-mRNA.

What is the initial state of a repressor in a repressible operon?

Inactive, meaning it cannot bind to the operator without a corepressor.

Which gene regulation mechanism helps prevent wasteful production of enzymes?

Inducible operons only express enzymes when substrate is present.

How does the regulation of enzymes contribute to bacterial survival?

It allows bacteria to conserve resources by producing only necessary proteins.

What are stem cells known for?

Their unique ability to differentiate into various cell types.

How do environmental signals contribute to cell differentiation?

They influence which genes are turned on or off in responding cells.

What is a major distinction between prokaryotic and eukaryotic gene regulation?

Prokaryotes utilize operons while eukaryotes require splicing and fine-tuning.

What is the ultimate result of transcription factors binding to enhancers?

It increases the likelihood of transcription of a connected gene.

What happens when glucose is absent and lactose is present?

CAP binds to cAMP and enhances transcription of lactose-utilizing genes.

What is the impact of anatomical layout in nuclear architecture?

It contributes to coordinated control of gene expression.

What does gene expression include?

Transcription, mRNA processing, translation, and regulation.

How do tumor suppressor genes prevent cell growth?

They repair DNA and control factors for cell division.

What occurs after mRNA is transcribed?

It undergoes processing to become mature mRNA.

What is an example of a positive regulatory control in prokaryotes?

The action of CAP when glucose is scarce.

How is protein synthesis regulated at the mRNA stage?

Through mRNA degradation and translational control by proteins.

What is the overall concept behind operon function?

Synchronized regulation of related genes to respond efficiently to environmental changes.

What effect does histone methylation have on transcription?

It typically inhibits transcription by compacting chromatin.

How can gene mutations lead to cancer?

By disrupting the normal regulation of the cell cycle and promoting unchecked growth.

What is the significance of control elements in transcription?

They help regulate when and how genes are expressed.

What are transcriptional factors known for in eukaryotic cells?

Facilitating or inhibiting the binding of RNA polymerase to DNA.