Biology Chapter on Gene Regulation

Questions and Answers

Which transcription factor is activated by fibrates and thiazolidinediones?

Leucine zipper proteins

Steroid receptors

cAMP response element binding protein

Peroxisome proliferator-activated receptors (correct)

What is the primary function of the cAMP response element binding protein (CREB)?

Regulate gene expression in response to cAMP (correct)

Respond to hormone signaling

Regulate lipid metabolism

Process mRNA splice variants

Which aspect of post-transcriptional regulation is directly influenced by the length of the poly-A tail?

mRNA stability (correct)

Alternative splicing

mRNA translation efficiency

miRNA targeting

In which tissue is the calcitonin gene known to produce different transcripts for distinct peptide products?

Thyroid gland Signup and view all the answers

What mechanism does miRNA use to affect mRNA?

Prevents mRNA translation Signup and view all the answers

What is the primary role of transcription factors in gene regulation?

They facilitate the binding of RNA polymerase to the promoter. Signup and view all the answers

Which structural feature is NOT characteristic of transcription factors?

Catalytic domain Signup and view all the answers

What is the effect of the lacI repressor when it is active?

It inhibits the binding of RNA polymerase. Signup and view all the answers

Which transcription factor is typically involved in the modulation of basal transcription in many genes?

SP-1 Signup and view all the answers

What type of transcription factors bind to enhancer regions to regulate transcription initiation?

Specific transcription factors Signup and view all the answers

Which of the following motifs allows transcription factors to interact with RNA polymerase?

Helix-loop-helix Signup and view all the answers

What is a common feature of both zinc finger and helix-turn-helix motifs?

Both bind to specific DNA sequences. Signup and view all the answers

What role do hormones play in the function of specific transcription factors?

They regulate the binding affinity of transcription factors. Signup and view all the answers

What is the role of enhancers in gene regulation?

To interact with regulatory proteins and increase expression rate Signup and view all the answers

Which transcription factor binds to the CCAAT box located around -75?

Nuclear factor I (NF-1) Signup and view all the answers

Which of the following describes constitutive gene expression?

Constant expression necessary for fundamental cellular functions Signup and view all the answers

What is the primary function of regulatory elements in gene expression?

To determine the conditions under which genes are expressed Signup and view all the answers

What distinguishes trans-elements from cis-elements?

Trans-factors are usually made by other genes and can regulate expression, whereas cis-elements are not Signup and view all the answers

What is a common function of silencers in gene regulation?

To decrease the rate of gene expression Signup and view all the answers

Which of the following describes other regulatory elements, such as hormone response elements (HRE)?

They mediate responses to various signals including hormones and chemicals Signup and view all the answers

What role does chromatin remodeling play in gene expression regulation?

It allows for the accessibility of DNA to transcription factors Signup and view all the answers

Which type of gene expression is characterized by genes that are activated only under specific conditions?

Inducible expression Signup and view all the answers

What is the main difference between general and specific transcription factors?

General factors regulate all genes, while specific factors only regulate particular genes. Signup and view all the answers

What characteristic feature distinguishes repressible genes?

They are turned off in response to specific signals. Signup and view all the answers

Which of the following examples best illustrates post-transcriptional regulation?

Modification of mRNA stability and translation efficiency Signup and view all the answers

How do housekeeping genes impact cellular function?

By maintaining essential cellular processes constantly Signup and view all the answers

What phenomenon explains why all cells with identical DNA can have different functions?

The regulation of gene expression Signup and view all the answers

What is the primary effect of acetylation on chromatin structure?

Leads to chromatin relaxation Signup and view all the answers

Which enzyme is responsible for the addition of acetyl groups to histones?

Histone acetyltransferases Signup and view all the answers

What is a primary biological role of methylation?

Repression of gene expression Signup and view all the answers

How does histone deacetylase (HDAC) affect gene expression?

It is associated with long-term gene repression Signup and view all the answers

Which type of DNA regulatory element is found proximal to the core promoter?

UPEs (Upstream Promoter Elements) Signup and view all the answers

What is the direct effect of chromatin condensation on gene expression?

Represses gene expression Signup and view all the answers

Which transcription factor is primarily associated with the activation of genes at the core promoter?

TFIID Signup and view all the answers

What is the significance of proximal regulatory elements in gene regulation?

They bind transcription factors to regulate expression Signup and view all the answers

Which of the following is NOT a role of histone methyltransferases?

Promotion of chromatin relaxation Signup and view all the answers

Which DNA modification is linked to genomic imprinting and X-inactivation?

Methylation of DNA Signup and view all the answers

Study Notes

Gene Regulation Overview

Gene expression is controlled through multiple mechanisms, including the binding of regulatory proteins such as transcription factors.
All cells contain the same DNA, but regulation mechanisms govern when, where, and how much gene product is produced.

Genes and Regulatory Proteins

lacI Repressor: Can prevent RNA synthesis when not bound by an inducer.
Transcription Factors (TF): Proteins with at least two essential domains; a DNA binding domain and an activating domain.
- Functions: Bind to specific motifs in promoters or enhancers to regulate transcription.
- Types: General transcription factors (e.g., TFIID) are necessary for RNA polymerase binding, while specific transcription factors (e.g., steroid receptors) modulate transcription in response to conditions.

Binding Motifs of Transcription Factors

Common DNA binding motifs include:
- Zinc fingers
- Leucine zippers
- Helix-loop-helix
- Helix-turn-helix

Transcription Factor Classes

General Transcription Factors: Bind to core promoters to initiate transcription (e.g., SP-1, NF-1).
Specific Transcription Factors: Bind to enhancers or silencers, affecting the rate of gene transcription. Can be tissue or cell-specific.

Post-Transcriptional Regulation

Splicing: Involves the modification of mRNA after transcription, allowing for diverse protein products from the same gene.
mRNA Stability: Influenced by the length of the poly-A tail; longer tails promote stability.
miRNA: Can bind target mRNA to inhibit translation.

Gene Expression Types

Constitutive Genes: Always active; essential for everyday cellular functions (e.g., GAPDH, HSP70).
Inducible Genes: Activated only under specific conditions (e.g., stress response proteins).
Repressible Genes: Can be turned off when not needed (e.g., ferritin in response to iron levels).

Chromatin Remodeling

Various modifications affect chromatin structure, including:
- Acetylation: Promotes gene expression by relaxing chromatin structure.
- Deacetylation: Represses gene expression by condensing chromatin.
- Methylation: Can silence gene expression, particularly when occurring at CpG sites in DNA.

Regulatory Elements

Basal Regulatory Elements: Serve as binding sites for transcription factors and are crucial for transcription initiation.
Enhancers and Silencers: DNA sequences that can increase (enhancers) or decrease (silencers) gene expression by interacting with trans-factors.

Sequence Elements in Regulation

Core Promoter Elements: Include the TATA box and are essential for transcription initiation.
Upstream Promoter Elements (UPE): Such as CAAT and GC-rich sequences, facilitate additional transcription factor binding.

Biological Roles of Gene Regulation

Gene regulation impacts cellular differentiation, the cell cycle, DNA repair, and various signal responses (e.g., to hormones).

Key Questions

Understand how transcription regulation varies among different cell types and conditions, including the roles of cis and trans regulatory elements in gene expression outcomes.

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Description

This quiz focuses on the mechanisms of gene regulation, specifically examining the lac operon and the roles of various elements such as the lacI repressor and RNA polymerase. Understand how these components interact to control gene expression and the synthesis of mRNA. Perfect for students looking to deepen their understanding of molecular biology.