EPIGENETICS

What is epigenesis?

The process by which gene expression in undifferentiated cells is changed without changing DNA sequence.

What are epigenetic tags?

Chemical modifications that turn genes ON or OFF without changing DNA sequence.

How does DNA methylation affect gene expression?

Methylation of cytosine in promoter regions silences gene transcription.

What is histone modification?

Chemical changes to histone tails that alter how tightly DNA is wrapped, affecting gene accessibility and transcription rate.

What is the genome?

All genetic material in a cell (coding + non-coding DNA).

What is the transcriptome?

All mRNA molecules in a cell at a given time.

What is the proteome?

All proteins produced by a cell.

How are genome, transcriptome, and proteome related?

Genome is fixed → transcriptome changes with gene expression → proteome depends on proteins translated from mRNA.

How can the environment affect gene expression?

Environmental factors (e.g. pollution) can change DNA methylation patterns, altering gene expression and development (e.g. fetal growth, birth mass).

What is epigenetic inheritance?

Transmission of gene expression patterns through epigenetic tags, without changing DNA sequence.

What is genomic imprinting?

When one parental allele is silenced by epigenetic tags, so only one allele is expressed.

What happens to epigenetic tags during gamete formation?

99% are removed, but some remain and can be inherited.

Why are ligers and tigons different sizes?

Different parental epigenetic imprints affect growth gene expression.

Why can identical twins differ?

Same genotype but different environments lead to different epigenetic tags and gene expression.

How is ABO blood group inherited?

• IA and IB are codominant

• i is recessive

• IAIB = AB (both antigens expressed)

What causes PKU?

Mutation in enzyme gene that breaks down phenylalanine → tyrosine.

What causes haemophilia? and why are males more affected?

Mutation in clotting gene on X chromosome.

And Males only have only one X chromosome.

What are recombinant offspring?

Offspring with new allele combinations due to crossing over in meiosis.

Why is epigenetics important?

It controls gene expression, affects phenotype, and can respond to environmental change without altering DNA.