Gene Expression Regulation: Methylation of Promoter Elements and Allelic Exclusion

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Questions and Answers

What is the primary mechanism by which methylation of promoter elements regulates gene expression?

By inducing a conformational change in the DNA molecule

By cleaving the DNA molecule at specific regions

By making it difficult for transcription factors to bind or by attracting other proteins to bind instead (correct)

By recruiting histone acetylases to activate transcription

What is the definition of allelic exclusion?

The inheritance of traits transmitted by mechanisms directly involving the nucleotide sequence

The random inactivation of one X chromosome in female mammals

The silencing of one allele of a gene while the other allele is expressed (correct)

The expression of both alleles of a gene in a single cell

What is genomic imprinting?

The random inactivation of one X chromosome in female mammals

The silencing of certain genes depending on which parent passes them on (correct)

The expression of both alleles of a gene in a single cell

The inheritance of traits transmitted by mechanisms directly involving the nucleotide sequence

What is the result of X-chromosome inactivation in female mammals?

The formation of a condensed structure called a Barr body Signup and view all the answers

What is the mechanism involved in X-chromosome inactivation?

DNA methylation and changes in chromatin structure Signup and view all the answers

What is the consequence of a female being heterozygous for a gene on her X chromosomes?

A mix of traits related to that gene, creating a mosaic pattern Signup and view all the answers

What is epigenetic inheritance?

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence Signup and view all the answers

What is the role of DNA methylation in genomic imprinting?

To silence certain genes depending on which parent passes them on Signup and view all the answers

What is the result of ATP → ADP releasing energy in nucleosomes?

Nucleosomes slide away from each other, exposing DNA regions. Signup and view all the answers

What is the function of chaperones in gene regulation?

To assist in forming, changing or rebuilding nucleosomes. Signup and view all the answers

What is the effect of histone acetylation on chromatin structure?

It loosens chromatin structure, promoting transcription. Signup and view all the answers

What is the role of methylation in genomic imprinting?

It regulates expression of either the maternal or paternal alleles. Signup and view all the answers

What is the consequence of DNA methylation on gene expression?

It reduces transcription, compacting chromatin structure. Signup and view all the answers

What is the effect of histone acetylation on histone tails?

It cancels out the positive charge, preventing tight DNA wrapping. Signup and view all the answers

What is the primary function of microRNA in gene regulation?

To block ribosomes from translating mRNA Signup and view all the answers

What is the result of ATP → ADP releasing energy in chromatin structure?

Chromatin structure becomes more loose, promoting transcription. Signup and view all the answers

Where are the nucleotide sequences found that influence the life span of mRNA in eukaryotes?

In the untranslated region (UTR) at the 3′ end of the mRNA Signup and view all the answers

What is the consequence of histone tail modification on gene expression?

It sends signals for gene regulation, depending on the modification. Signup and view all the answers

What is the term for the loosely packed chromatin in the nucleus during interphase?

Euchromatin Signup and view all the answers

What is the result of the dense packing of heterochromatin?

Makes it difficult for the cell to express genetic information Signup and view all the answers

What is the function of chromatin remodelers?

To bind the nucleosome of DNA and use energy from ATP to remodel chromatin Signup and view all the answers

How many ways are chromatin structure regulated?

2 ways Signup and view all the answers

What is the term for the chromatin fiber folded into loops?

Solenoid fibers Signup and view all the answers

What are the three types of chromatin remodelers?

Chromatin remodelling complex, chaperons, and chemical modification Signup and view all the answers

Study Notes

Gene Expression Regulation and Epigenetics

Methylation of promoter elements shuts down transcription by making it difficult for factors to bind or by attracting other proteins to bind instead.

Allelic Exclusion

Only one allele of a gene is expressed while the other allele is silenced.
Examples: Genomic Imprinting and X-Chromosome Inactivation.

Genomic Imprinting

Silencing of certain genes depending on which parent passes them on.
Imprinting is the result of the methylation of cytosine nucleotides.

X-Chromosome Inactivation

In female mammals, one of their two X chromosomes is randomly turned off during embryonic development.
The turned-off X forms a condensed structure called a Barr body.
This process involves DNA methylation and changes in chromatin structure.

Epigenetic Inheritance

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.

Chromatin and Epigenetic Regulation

Chromatin = DNA + protein.
Most chromatin is loosely packed in the nucleus during interphase.
Chromatin condenses prior to mitosis.
Loosely packed chromatin is called euchromatin (nucleosomes aren’t close together).
Highly condensed chromatin regions (centromeres and telomeres) are called heterochromatin.
Dense packing of heterochromatin makes it difficult for the cell to express genetic information coded in these regions.

Chromatin Remodelers

Chromatin remodelers: Chromatin remodelling complex, Chaperons, and Chemical Modification.
Chromatin remodelling complex: enzymes that use energy from ATP to bind to the nucleosome of DNA.
Chaperons: proteins that assist in forming, changing or rebuilding nucleosomes.
Chemical Modification: changing histone proteins tails with chemical modifications like methylation, phosphorylation, or acetylation.

Histone Acetylation and Methylation

Histone acetylation: adding acetyl groups (-ve charge) to an amino acid in a histone tail, opens up the chromatin structure, making it more loosely packed.
Histone methylation: promotes DNA wrapping, reducing transcription, and can permanently silence genes during cellular development.

Micro RNA and mRNA

Micro RNA can lead to mRNA degradation.
Micro RNA sticks to mRNA with matching sequences, blocking ribosomes and stopping translation.

Nucleotide Sequence and mRNA Life Span

Nucleotide sequences that influence the life span of mRNA in eukaryotes reside in the untranslated region (UTR) at the 3′ end of the molecule.

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Description

Learn about the role of methylation in promoter elements in gene expression regulation and allelic exclusion, where only one allele of a gene is expressed. Understand how methylation affects transcription and factors binding.