24 Questions
What is the primary mechanism by which methylation of promoter elements regulates gene expression?
By making it difficult for transcription factors to bind or by attracting other proteins to bind instead
What is the definition of allelic exclusion?
The silencing of one allele of a gene while the other allele is expressed
What is genomic imprinting?
The silencing of certain genes depending on which parent passes them on
What is the result of X-chromosome inactivation in female mammals?
The formation of a condensed structure called a Barr body
What is the mechanism involved in X-chromosome inactivation?
DNA methylation and changes in chromatin structure
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
What is epigenetic inheritance?
The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
What is the role of DNA methylation in genomic imprinting?
To silence certain genes depending on which parent passes them on
What is the result of ATP → ADP releasing energy in nucleosomes?
Nucleosomes slide away from each other, exposing DNA regions.
What is the function of chaperones in gene regulation?
To assist in forming, changing or rebuilding nucleosomes.
What is the effect of histone acetylation on chromatin structure?
It loosens chromatin structure, promoting transcription.
What is the role of methylation in genomic imprinting?
It regulates expression of either the maternal or paternal alleles.
What is the consequence of DNA methylation on gene expression?
It reduces transcription, compacting chromatin structure.
What is the effect of histone acetylation on histone tails?
It cancels out the positive charge, preventing tight DNA wrapping.
What is the primary function of microRNA in gene regulation?
To block ribosomes from translating mRNA
What is the result of ATP → ADP releasing energy in chromatin structure?
Chromatin structure becomes more loose, promoting transcription.
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
What is the consequence of histone tail modification on gene expression?
It sends signals for gene regulation, depending on the modification.
What is the term for the loosely packed chromatin in the nucleus during interphase?
Euchromatin
What is the result of the dense packing of heterochromatin?
Makes it difficult for the cell to express genetic information
What is the function of chromatin remodelers?
To bind the nucleosome of DNA and use energy from ATP to remodel chromatin
How many ways are chromatin structure regulated?
2 ways
What is the term for the chromatin fiber folded into loops?
Solenoid fibers
What are the three types of chromatin remodelers?
Chromatin remodelling complex, chaperons, and chemical modification
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.
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.
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