Lecture 5 - Epigenetic's Flashcards
What is epigenetics?
Epigenetics is the study of heritable changes in gene expression and function that do not involve changes in the DNA sequence.
How do epigenetic changes affect gene expression?
They modify DNA or histones with chemical tags, like methyl or acetyl groups, to regulate transcription.
What is the epigenome?
The epigenome is the collection of all chemical tags attached to the DNA of a cell, influencing gene expression.
How can epigenetics explain why genetically identical twins can differ as they age?
Environmental factors cause epigenetic changes that diverge over time, affecting gene expression and traits.
What is DNA methylation?
The addition of a methyl group to cytosine, typically at CpG sites, by writer enzymes.
How does DNA methylation affect transcription?
It inhibits transcription by blocking transcription factor binding or recruiting repressor proteins.
What ensures the maintenance of methylation during DNA replication?
Reader proteins recruit writer enzymes to restore methylation on the newly synthesised strand.
Why is DNA methylation considered a reversible modification?
It can be removed by eraser enzymes, allowing dynamic regulation of gene expression.
What are the major types of histone modifications?
Acetylation, methylation, phosphorylation, and ubiquitination.
How does histone acetylation affect gene expression?
Acetylation reduces the positive charge on histones, loosening chromatin and promoting transcription.
What is the effect of H3K27me3 on gene expression?
It condenses chromatin, silencing transcription.
How are histone modifications maintained during DNA replication?
Parental histones distribute equally between daughter strands, and marks are restored on new histones by writer enzymes.
What is the histone code?
A hypothesis that combinations of histone modifications act as a code, interpreted by reader proteins to regulate gene expression.
What is mitotic inheritance of epigenetic marks?
Epigenetic marks are maintained during cell division, allowing daughter cells to retain the gene expression patterns of the parent cell.
How is epigenetic inheritance different in plants and animals?
Epigenetic marks are largely erased in animal gametes but are often retained in plants, allowing transgenerational inheritance.
What happens if erasure of epigenetic marks in gametes is incomplete?
Some marks can be passed to the next generation, leading to transgenerational inheritance.
How does the environment influence the epigenome?
Factors like diet, stress, chemicals, and social interactions can alter epigenetic tags, affecting gene expression.
What is the role of DNA methylation in stress response in rats?
Lack of maternal care can lead to methylation of stress-regulating genes, silencing them and affecting stress management.
How do epigenetics guide cell differentiation?
By activating or silencing genes, epigenetic changes allow cells with identical genomes to develop into distinct cell types.
Why are epigenetic marks essential during development?
They ensure specific genes are expressed or silenced in different tissues, maintaining proper function.
How does epigenetics regulate queen and worker bee development?
Worker jelly increases DNA methylation, altering gene expression and splicing, while royal jelly reduces methylation, promoting queen-specific gene expression.
What is the role of phenolics in bee development?
Phenolics in worker jelly modulate DNA methylation and splicing, influencing bee caste development.
What is haplodiploid sex determination in bees?
Males are haploid and develop from unfertilised eggs, while females are diploid and develop from fertilised eggs.
What is the significance of H3K27me3 in plants?
It is a histone modification that silences the FLC gene in seeds, resetting epigenetic marks each generation.
How are nucleosomes reassembled during DNA replication?
Parental histones are split between daughter strands, and new histones from the cytosol are modified to match parental marks.
What mechanisms ensure accurate inheritance of histone marks?
Reader proteins recognise parental marks and recruit writer proteins to replicate them on new histones.
What are reader, writer, and eraser proteins in epigenetics?
Readers: Recognise and bind to epigenetic marks.
Writers: Add epigenetic marks.
Erasers: Remove epigenetic marks.
How does DNA methylation differ between prokaryotes and eukaryotes?
It is present in both, but in eukaryotes, it plays a more significant role in gene regulation and development.
How does histone acetylation affect the electrostatic attraction between DNA and histones?
Acetylation neutralises the positive charge on histones, reducing their attraction to negatively charged DNA and promoting a looser chromatin structure.
What is the significance of H3K4me3 in gene expression?
H3K4me3 is associated with transcriptional activation, promoting an open chromatin structure for active gene expression.
How can epigenetics lead to disease?
Epigenetic changes, such as methylation of tumour-suppressor genes, can silence their expression, contributing to cancer development.
What is the role of epigenetic eraser proteins in gamete formation?
Eraser proteins remove most epigenetic marks to reset the genome, allowing proper gene expression in the next generation.
How do epigenetic changes influence gene splicing in bees?
Methylation levels affect exon inclusion or skipping, producing different protein isoforms that contribute to caste determination.
What are examples of non-coding RNAs involved in epigenetics?
Small and long non-coding RNAs, such as siRNAs and lncRNAs, can regulate transcription and translation through interactions with chromatin or mRNA.
