Lecture 17 Review
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Questions and Answers

What role do chromatin remodeling complexes play in gene expression?

  • They regulate chromatin structure. (correct)
  • They modify the DNA sequence.
  • They enhance protein synthesis.
  • They directly synthesize RNA.

Which process is NOT a mechanism of gene expression regulation?

  • DNA methylation
  • Histone modification
  • Chromatin remodeling
  • RNA splicing (correct)

What is the concept of a 'master regulator' in gene expression?

  • A protein that regulates the expression of multiple genes. (correct)
  • A mutation that disrupts normal gene function.
  • An enzyme that synthesizes RNA from DNA.
  • A gene that operates independently of others.

How does DNA methylation contribute to cellular memory?

<p>Through positive feedback and stable inheritance of gene expression states. (A)</p> Signup and view all the answers

Which of the following best describes transcriptional regulators?

<p>They operate as a coordinated group to control transcription. (D)</p> Signup and view all the answers

Which mechanism does NOT influence chromatin structure?

<p>Nucleotide substitution (B)</p> Signup and view all the answers

What is the primary function of enhancers in gene regulation?

<p>To enhance the rate of transcription initiation. (A)</p> Signup and view all the answers

Which factor is NOT essential for the action of transcriptional regulators?

<p>Presence of amino acids (B)</p> Signup and view all the answers

What role do activators play in transcription regulation?

<p>They turn transcription 'ON'. (C)</p> Signup and view all the answers

How does DNA methylation affect gene expression?

<p>It condenses chromatin and represses gene expression. (C)</p> Signup and view all the answers

Which enzyme is responsible for adding histone modifications?

<p>Histone acetyltransferase (A)</p> Signup and view all the answers

What effect does tight packing of chromatin have on transcription?

<p>Inhibits transcription. (C)</p> Signup and view all the answers

What is the consequence of unmethylated CpG islands in mammalian genes?

<p>They activate gene expression by decondensing chromatin. (C)</p> Signup and view all the answers

How can combinations of transcriptional regulators affect cell type development?

<p>They can generate many specialized cell types during development. (A)</p> Signup and view all the answers

What is the function of chromatin remodeling complexes in gene regulation?

<p>They facilitate the physical rearrangement of chromatin structure. (D)</p> Signup and view all the answers

What outcome is associated with methylated CpG islands?

<p>They recruit proteins that repress transcription. (D)</p> Signup and view all the answers

How do positive feedback loops contribute to cell memory?

<p>By activating transcription of protein A and other cell fate control genes (D)</p> Signup and view all the answers

What is the role of histone modifying enzymes in cell memory?

<p>They alter histone modifications that are transferred to daughter cells. (A)</p> Signup and view all the answers

Which statement about DNA methylation is true?

<p>It is transmitted between generations by maintenance methyltransferase. (A)</p> Signup and view all the answers

What distinguishes epigenetic inheritance from genetic inheritance?

<p>It passes down gene expression patterns without altering the DNA sequence. (B)</p> Signup and view all the answers

In female mammals, how is dosage compensation achieved?

<p>Through random inactivation of one X chromosome. (A)</p> Signup and view all the answers

What is the effect of X inactivation in female mammals?

<p>It can alter the phenotype by creating a balance of expressed alleles. (C)</p> Signup and view all the answers

Which mechanism is primarily responsible for passing down histone modifications?

<p>Histone modifying enzymes (C)</p> Signup and view all the answers

What is a key feature of epigenetic changes in relation to genetic code?

<p>They are reversible and do not affect nucleotide sequences. (D)</p> Signup and view all the answers

Flashcards

Nucleosome

A complex of DNA tightly wound around histone proteins, forming the basic unit of chromatin.

Chromatin

The structural unit of chromosomes consisting of DNA packaged with histone proteins.

Chromatin remodeling complexes

Proteins that bind to DNA and influence gene expression by altering chromatin structure.

Histone modification enzymes

Enzymes that add or remove chemical modifications to histone proteins, influencing chromatin structure and gene expression.

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DNA methylation

A mechanism of gene regulation where a methyl group is added to the DNA sequence, altering gene expression.

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Master regulator

A gene that controls the expression of many other genes, often involved in cellular identity and differentiation.

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Cell memory

The ability of a cell to maintain a stable gene expression pattern across generations, even after the initial trigger for that pattern is removed.

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Positive feedback loop

A mechanism of cell memory where the product of a gene activates its own expression, creating a self-perpetuating loop.

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Chromatin Remodeling

The process of altering the structure of chromatin, making it more or less accessible to transcription factors.

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Histone Modifying Enzymes

Enzymes that attach chemical modifications to histone proteins, influencing chromatin structure and gene expression.

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Transcriptional Regulators

Specialized proteins that bind to specific DNA sequences and control the transcription of genes.

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Activators

Transcriptional regulators that increase the rate of gene transcription.

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Repressors

Transcriptional regulators that decrease the rate of gene transcription.

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CpG Islands

Regions in DNA that contain a high concentration of CpG dinucleotides (cytosine followed by guanine).

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Maintaining Cell Identity

The process by which cells maintain their unique gene expression patterns over time, ensuring that differentiated cells retain their identity.

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Histone modifications

Chemical modifications to histones, the proteins that DNA wraps around, which can affect gene expression. These modifications are heritable.

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Epigenetic inheritance

The inheritance of gene expression patterns without changes to the DNA sequence itself. These patterns are often maintained through histone modifications and DNA methylation.

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Dosage compensation

A mechanism that ensures equal expression of X-linked genes in males and females, even though they have different numbers of X chromosomes. In mammals, this is achieved by randomly inactivating one X chromosome in females.

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X inactivation

A phenomenon where female mammals inherit two X chromosomes but randomly inactivate one, resulting in a mosaic of cells with different active X chromosomes.

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Epigenetic mechanisms

A process that establishes long-term changes in gene expression patterns, making them irreversible and heritable. This is crucial for cell memory and differentiation.

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Study Notes

Gene Expression Regulation

  • Chromatin structure is regulated by chromatin remodeling complexes, histone modification enzymes, and DNA methylation which affect gene expression.
  • "Master regulators" are crucial for development.
  • Cell memory can result from positive feedback.

Exam Information

  • Exams are administered via CANVAS.
  • Check CANVAS for exam instructions and new seat assignments by November 8th.
  • Exam material will be from lectures 14-18 and sections 8-9.

Differential Gene Expression

  • Differential gene expression creates cell diversity and controls when genes are active.
  • DNA regulatory modules determine expression of genes in specific cell types at different stages of development.
  • DNA looping and protein-protein interactions facilitate RNA polymerase initiation of transcription.

Transcriptional Regulators

  • Activators and repressors are protein regulators of gene expression.
  • Regulators display DNA sequence specificity and function individually or in combination.
  • Transcriptional regulators work together like a committee to precisely control gene expression during specific stages of cell development.

Chromatin Structure and Transcription

  • Tight chromatin organization restricts access to DNA for transcription machinery.
  • Chromatin remodeling complexes use ATP to loosen DNA and reposition nucleosomes along the histone octamer.
  • Histone modification enzymes alter chromatin structure via covalent modifications.
  • DNA methylation can alter chromatin structure and repress gene expression.

Histone Modifying Enzymes

  • Histone modifying enzymes can modify histone tails by acetylation, methylation, and other covalent modifications to affect gene expression by either activating or repressing gene expression.
  • Specific histone modifications can recruit chromatin remodeling proteins and influence transcription.

DNA Methylation

  • DNA methylation can affect chromatin structure and repress gene expression.
  • CpG islands play a role in gene expression in mammals, with methylation often associated with gene repression.
  • Methylation patterns can be transmitted during DNA replication.

Cell Memory

  • Positive feedback loops maintain cell identity.
  • Histone modifications and DNA methylation can transmit patterns to daughter cells.

Epigenetic Inheritance

  • Epigenetic inheritance involves the transmission of gene expression patterns through generations without modifying DNA sequence.

Dosage Compensation

  • Dosage compensation equalizes X chromosome gene expression in males and females.
  • In mammals, X chromosome inactivation in females is an example of dosage compensation.

Next Lecture

  • The next lecture is on cell signaling.

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L17 Regulation of Gene Expression - F2024 Exam Notes PDF

Description

This quiz covers key concepts in gene expression regulation including chromatin structure, differential gene expression, and transcriptional regulators. It highlights the importance of master regulators in development and the mechanisms that create cell diversity. Prepare for exams based on lectures 14-18 and sections 8-9.

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