Gene Expression Regulation in Eukaryotes

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Questions and Answers

What is the primary reason for the regulation of gene expression in multicellular organisms?

To prevent mutations from occurring within the genome.

To increase the amount of DNA within the cells.

To allow different cells to perform specialized functions by expressing different sets of genes. (correct)

To ensure that all cells express all genes at all times.

Approximately what percentage of protein-coding genes might a typical human cell express at any given time?

80%

100%

20% (correct)

What term is used to describe the expression of different genes by cells with the same genome?

Genetic mutation

Differential gene expression (correct)

Cellular differentiation

Genome amplification

Which of the following is an example of information from inside the cell that can affect gene expression?

The amount of ATP (D) Signup and view all the answers

Which of the following can come from outside the cell to influence gene expression?

Chemical signals from other cells (C) Signup and view all the answers

What is the role of growth factors in regulating gene expression?

They activate a signaling pathway that leads to the transcription of specific genes. (C) Signup and view all the answers

What is the primary function of a repressor in the context of gene expression?

To block activators from binding to enhancers, thus inhibiting gene expression. (B) Signup and view all the answers

What is the role of transcription factors in gene expression?

They bind to DNA to promote or inhibit transcription. (B) Signup and view all the answers

In eukaryotic cells, what primarily dictates the high levels of transcription for specific genes?

The interaction between control elements and specific transcription factors. (B) Signup and view all the answers

What does the process of differential gene expression lead to?

The development of specialized cells with distinct functions. (C) Signup and view all the answers

Which of the following is NOT a main type of post-transcriptional regulation?

mRNA Degradation in the nucleus (B) Signup and view all the answers

What is the impact of a longer poly-A tail on mRNA stability?

It increases mRNA stability, allowing for more protein production. (C) Signup and view all the answers

How does the lifespan of mRNA differ between prokaryotes and eukaryotes?

Prokaryotic mRNA has a shorter lifespan, lasting seconds, while eukaryotic mRNA can last from hours to weeks. (D) Signup and view all the answers

How do regulatory proteins prevent the initiation of translation?

By binding to the 5' or 3' end of the mRNA and preventing ribosome attachment. (D) Signup and view all the answers

What is the role of proteasomes in the cell?

To bind to protein molecules and degrade them. (A) Signup and view all the answers

Which of the following is directly used to measure gene expression?

The amount of functional protein. (B) Signup and view all the answers

Which of the following best describes the relationship between chromosomes and chromatin?

Chromosomes are the tightly coiled DNA around proteins during cell division, while chromatin is the loosely packed DNA around proteins. (C) Signup and view all the answers

What is the primary function of histones in DNA structure?

To provide a structural framework around which DNA can be wrapped, allowing for compaction. (D) Signup and view all the answers

Which of the following is a key difference between heterochromatin and euchromatin?

Heterochromatin is more tightly packed, preventing transcription, while euchromatin is more loosely packed, allowing for transcription. (B) Signup and view all the answers

What impact does histone acetylation generally have on gene expression?

It creates loosely packed DNA (euchromatin), which makes transcription more likely. (C) Signup and view all the answers

What is the typical consequence of DNA methylation in eukaryotic gene expression?

It typically leads to long term inactivation of the DNA segments. (D) Signup and view all the answers

What is the primary characteristic of epigenetic inheritance?

The transmission of traits through mechanisms not involving changes in the DNA sequence. (B) Signup and view all the answers

Which component of the transcription initiation complex is responsible for binding to specific DNA sequences?

Transcription factors (C) Signup and view all the answers

What is the role of an enhancer in the process of eukaryotic gene expression?

To serve as a binding site for activator proteins to regulate the transcription of a gene. (D) Signup and view all the answers

What percentage of the human genome is comprised of protein-coding DNA?

1.5% (B) Signup and view all the answers

Which of the following is NOT a type of non-protein-coding RNA involved in gene expression regulation?

rRNA (B) Signup and view all the answers

What is the primary mechanism of action of microRNAs (miRNAs)?

To degrade mRNA or block translation (D) Signup and view all the answers

What structure is formed by mRNA folding on itself during miRNA regulation?

Double-stranded RNA (B) Signup and view all the answers

What is the primary function of short interfering RNAs (siRNAs)?

To block gene expression with sequence similarity (B) Signup and view all the answers

What do both miRNAs and siRNAs have in common regarding gene expression?

They both use similar proteins and block gene expression (C) Signup and view all the answers

Prior to recent research, what was the majority of 'non-protein coding DNA' often considered?

Un-transcribed 'junk' DNA (C) Signup and view all the answers

What type of enzyme is involved in the processing of dsRNA formed by miRNA base pairing with mRNA?

An enzyme that digests the dsRNA (B) Signup and view all the answers

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Study Notes

Regulation of Gene Expression in Eukaryotes

All cells in an organism contain the entire DNA, but only specific genes are turned on in each cell type.
Genes expressed determine a cell's function, like liver enzymes produced by liver cells, unlike those in stomach cells.
A typical human cell expresses approximately 20% of its protein-coding genes at any given time.
Specialized cells, such as muscle and nerve cells, express even fewer genes.
However, every cell contains a complete genome, differing only in which genes are expressed.
Cell type differences arise due to differential gene expression, the expression of different genes by cells with the same genome.
Gene expression can lead to diseases such as cancer due to abnormalities.
Gene expression is regulated at multiple stages.

How Cells "Decide" Which Genes to Turn On

Cell types and their specific environment/internal states influence gene expression patterns.
Gene expression is influenced by information from both inside and outside the cell.
Intracellular information includes proteins inherited from parent cells, DNA damage status, and available ATP.
Extracellular information consists of cell signaling, mechanical signals from the extracellular matrix, and nutrient availability.

Chromatin Structure Regulation

Chromosomes are tightly compacted DNA around proteins during cell division.
Chromatin is less tightly packed DNA around proteins.
Histones are proteins around which DNA wraps.
Nucleosomes are grouped histones together.
Heterochromatin is tightly packed chromatin, reducing transcription.
Euchromatin is loosely packed chromatin, allowing transcription.

Regulation of Transcription Initiation

Transcription involves RNA polymerase II and transcription factors.
RNA polymerase II attaches to the promoter (TATA box) to start transcription.
Control elements are non-coding DNA sequences where transcription factors bind.
Enhancers are control elements far from a gene that can turn transcription on or off.
Activators bind to enhancers to activate a gene's transcription
Repressors hinder gene expression by blocking activators from binding to enhancers.

Post-Transcriptional Regulation

Gene expression isn't solely determined by transcription, but also by mRNA processing, degradation, translation initiation, and protein processing/degradation.
RNA processing involves the addition of a cap, a poly-A tail, and the removal of introns. Alternative RNA splicing can result.
mRNA Degradation affects the duration it's available for translation, and is influenced by its poly-A tail length. In prokaryotes, mRNA has a short life, while in eukaryotes it has a longer life span.
Initiation of Translation is regulated by proteins binding to mRNA, affecting ribosome attachment.
Protein Processing and Degradation involve modifications and breakdown of proteins to create functional molecules.
Proteasomes are giant protein complexes that degrade proteins.

Noncoding RNAs and Gene Expression Regulation

Non-protein-coding DNA in cells plays a role in gene expression.
microRNAs (miRNAs) can degrade mRNA or block its translation.
RNA interference (RNAi) and small interfering RNAs (siRNAs) function similarly to miRNAs, associating with proteins to block gene expression.

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Description

This quiz explores the intricacies of gene expression regulation in eukaryotic cells. It delves into how different cell types activate specific genes while maintaining the same genetic code, and examines the implications of these processes on cell function and potential diseases. Test your understanding of how gene expression is influenced by various factors and its complexity.