BLOCK 6 - genetics

What is epigenetics?

Regulation of gene expression without changing DNA sequence.

What is the key idea of epigenetics?

Same DNA, different gene expression.

Does epigenetics change genotype?

No.

What does epigenetics affect?

Phenotype.

What are histones?

Proteins DNA wraps around.

What do histone modifications control?

DNA accessibility.

What does acetylation do?

Opens chromatin.

How does acetylation affect DNA binding?

Reduces positive charge → weaker DNA binding.

What is the effect of acetylation on transcription?

Increases gene expression.

What is histone methylation?

Addition of CH₃ group.

Does methylation always repress genes?

No.

What determines the effect of methylation?

Which amino acid is modified.

What is H3K9me3 associated with?

Gene repression (heterochromatin).

What is euchromatin?

Loosely packed, active genes.

What is heterochromatin?

Tightly packed, inactive genes.

How can you remember euchromatin and heterochromatin?

Eu = Expressed, Hetero = Hidden.

What is DNA methylation?

Addition of methyl group to cytosine.

Where does methylation occur?

CpG sites.

What is 5mC?

Methylated cytosine.

What is the effect of promoter methylation?

Gene silencing.

What are CpG islands?

Regions controlling gene expression.

What role does DNA methylation play in gene regulation?

Silences genes.

What role does DNA methylation play in genome defence?

Stops transposable elements.

What are transposable elements?

Jumping genes.

What is siRNA?

Small interfering RNA.

What does siRNA do?

Degrades mRNA.

What is the result of siRNA action?

Prevents protein production.

What factors affect epigenetics?

Diet, stress, pollution, temperature.

Can the environment change gene expression?

Yes.

What is transgenerational inheritance?

Epigenetic traits passed to offspring.

Are epigenetic marks always inherited?

No, often reset.

Can epigenetics affect mutation?

Yes.

What is an example of epigenetics affecting mutation?

5mC → C to T mutation.

What mutates frequently?

CpG sites.

What is imprinting?

Only one allele expressed depending on parent.

What controls imprinting?

Epigenetic marks (not DNA changes).

What are ICRs?

Imprinting control regions.

What is the epigenetic clock?

Biological age based on methylation.

How do biological and chronological age differ?

Not always the same.

What does ChIP-Seq detect?

Histone modifications.

What are the key steps in ChIP-Seq?

Antibody binds → DNA pulled → sequencing.

What does RNA-Seq measure?

All RNA expression.

What types of RNA does RNA-Seq measure?

mRNA, lncRNA, small RNAs.

Why is rRNA removed in RNA-Seq?

To focus on functional RNAs.

What does bisulfite do?

Converts unmethylated C → T.

What happens to methylated C in bisulfite treatment?

Remains C.

Why is bisulfite treatment useful?

Detects methylation at single-base level.

How does nanopore sequencing work?

DNA passes through pore → current changes.

What is an advantage of nanopore sequencing?

Detects methylation directly.

Does nanopore sequencing require chemical treatment?

No.

What is the effect of acetylation on gene expression?

Gene ON.

What is the effect of methylation on gene expression?

Gene ON or OFF (context-dependent).

What is the usual effect of DNA methylation?

Gene OFF.

What does euchromatin indicate?

Active genes.

What does heterochromatin indicate?

Silent genes.

Does epigenetics involve changes in DNA sequence?

No.

What are the main mechanisms of epigenetics?

Histones + DNA methylation.

How does the environment influence the epigenome?

It can cause epigenetic changes.

How can epigenetic changes influence disease?

They can alter gene expression related to disease.