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Genetics and Evolution > Lecture 5 - Epigenetic's > Flashcards

Lecture 5 - Epigenetic's Flashcards

1
Q

What is epigenetics?

A

Epigenetics is the study of heritable changes in gene expression and function that do not involve changes in the DNA sequence.

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2
Q

How do epigenetic changes affect gene expression?

A

They modify DNA or histones with chemical tags, like methyl or acetyl groups, to regulate transcription.

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3
Q

What is the epigenome?

A

The epigenome is the collection of all chemical tags attached to the DNA of a cell, influencing gene expression.

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4
Q

How can epigenetics explain why genetically identical twins can differ as they age?

A

Environmental factors cause epigenetic changes that diverge over time, affecting gene expression and traits.

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5
Q

What is DNA methylation?

A

The addition of a methyl group to cytosine, typically at CpG sites, by writer enzymes.

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6
Q

How does DNA methylation affect transcription?

A

It inhibits transcription by blocking transcription factor binding or recruiting repressor proteins.

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7
Q

What ensures the maintenance of methylation during DNA replication?

A

Reader proteins recruit writer enzymes to restore methylation on the newly synthesised strand.

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8
Q

Why is DNA methylation considered a reversible modification?

A

It can be removed by eraser enzymes, allowing dynamic regulation of gene expression.

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9
Q

What are the major types of histone modifications?

A

Acetylation, methylation, phosphorylation, and ubiquitination.

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10
Q

How does histone acetylation affect gene expression?

A

Acetylation reduces the positive charge on histones, loosening chromatin and promoting transcription.

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11
Q

What is the effect of H3K27me3 on gene expression?

A

It condenses chromatin, silencing transcription.

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12
Q

How are histone modifications maintained during DNA replication?

A

Parental histones distribute equally between daughter strands, and marks are restored on new histones by writer enzymes.

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13
Q

What is the histone code?

A

A hypothesis that combinations of histone modifications act as a code, interpreted by reader proteins to regulate gene expression.

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14
Q

What is mitotic inheritance of epigenetic marks?

A

Epigenetic marks are maintained during cell division, allowing daughter cells to retain the gene expression patterns of the parent cell.

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15
Q

How is epigenetic inheritance different in plants and animals?

A

Epigenetic marks are largely erased in animal gametes but are often retained in plants, allowing transgenerational inheritance.

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16
Q

What happens if erasure of epigenetic marks in gametes is incomplete?

A

Some marks can be passed to the next generation, leading to transgenerational inheritance.

17
Q

How does the environment influence the epigenome?

A

Factors like diet, stress, chemicals, and social interactions can alter epigenetic tags, affecting gene expression.

18
Q

What is the role of DNA methylation in stress response in rats?

A

Lack of maternal care can lead to methylation of stress-regulating genes, silencing them and affecting stress management.

19
Q

How do epigenetics guide cell differentiation?

A

By activating or silencing genes, epigenetic changes allow cells with identical genomes to develop into distinct cell types.

20
Q

Why are epigenetic marks essential during development?

A

They ensure specific genes are expressed or silenced in different tissues, maintaining proper function.

21
Q

How does epigenetics regulate queen and worker bee development?

A

Worker jelly increases DNA methylation, altering gene expression and splicing, while royal jelly reduces methylation, promoting queen-specific gene expression.

22
Q

What is the role of phenolics in bee development?

A

Phenolics in worker jelly modulate DNA methylation and splicing, influencing bee caste development.

23
Q

What is haplodiploid sex determination in bees?

A

Males are haploid and develop from unfertilised eggs, while females are diploid and develop from fertilised eggs.

24
Q

What is the significance of H3K27me3 in plants?

A

It is a histone modification that silences the FLC gene in seeds, resetting epigenetic marks each generation.

25
Q

How are nucleosomes reassembled during DNA replication?

A

Parental histones are split between daughter strands, and new histones from the cytosol are modified to match parental marks.

26
Q

What mechanisms ensure accurate inheritance of histone marks?

A

Reader proteins recognise parental marks and recruit writer proteins to replicate them on new histones.

27
Q

What are reader, writer, and eraser proteins in epigenetics?

A

Readers: Recognise and bind to epigenetic marks.

Writers: Add epigenetic marks.

Erasers: Remove epigenetic marks.

28
Q

How does DNA methylation differ between prokaryotes and eukaryotes?

A

It is present in both, but in eukaryotes, it plays a more significant role in gene regulation and development.

29
Q

How does histone acetylation affect the electrostatic attraction between DNA and histones?

A

Acetylation neutralises the positive charge on histones, reducing their attraction to negatively charged DNA and promoting a looser chromatin structure.

30
Q

What is the significance of H3K4me3 in gene expression?

A

H3K4me3 is associated with transcriptional activation, promoting an open chromatin structure for active gene expression.

31
Q

How can epigenetics lead to disease?

A

Epigenetic changes, such as methylation of tumour-suppressor genes, can silence their expression, contributing to cancer development.

32
Q

What is the role of epigenetic eraser proteins in gamete formation?

A

Eraser proteins remove most epigenetic marks to reset the genome, allowing proper gene expression in the next generation.

33
Q

How do epigenetic changes influence gene splicing in bees?

A

Methylation levels affect exon inclusion or skipping, producing different protein isoforms that contribute to caste determination.

34
Q

What are examples of non-coding RNAs involved in epigenetics?

A

Small and long non-coding RNAs, such as siRNAs and lncRNAs, can regulate transcription and translation through interactions with chromatin or mRNA.

Genetics and Evolution (30 decks)

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