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A1.1 Water

A1.2 Nucleic acids

A2.1 Origins of cells (HL)

A2.2 Cell structure

A2.3 Viruses (HL)

A3.1 Diversity of organisms

A3.2 Classification and cladistics (HL)

A4.1 Evolution and speciation

A4.2 Conservation of biodiversity

B1.1 Carbohydrates and lipids

B1.2 Proteins

B2.1 Membranes and membrane transport

B2.2 Organelles and compartmentalization

B2.3 Cell specialization

B3.1 Gas exchange

B3.2 Transport

B3.3 Muscle and motility (HL)

B4.1 Adaptation to environment

B4.2 Ecological niches

C1.1 Enzymes and metabolism

C1.2 Cell respiration

C1.3 Photosynthesis

C2.1 Chemical signalling (HL)

C2.2 Neural signalling

C3.1 Integration of body systems

C3.2 Defense against disease

C4.1 Populations and communities

C4.2 Transfer of energy and matter

D1.1 DNA replication

D1.2 Protein synthesis

D1.3 Mutations and gene editing

D2.1 Cell and nuclear division

D2.2 Gene expression (HL)

D2.3 Water potential

D3.1 Reproduction

D3.2 Inheritance

D3.3 Homeostasis

D4.1 Natural selection

D4.2 Sustainability and change

D4.3 Climate change

IB
D2.2.7 Epigenetic inheritance through heritable changes to gene expression

IB Biology Topic D2.2.7: Epigenetic Inheritance Through Heritable Changes to Gene Expression Key Definitions

D2.2.7 Epigenetic inheritance through heritable changes to gene expression Key Definitions

Definition

DNA methylation

DNA methylation involves the addition of a methyl group (–CH₃) to a cytosine base in DNA.

Definition

Epigenetic tag

An epigenetic tag is a chemical modification to DNA or histone proteins that regulates gene expression without altering the underlying DNA sequence.

Definition

Histone

A protein that provides structural support for DNA in eukaryotic cells. Histones are positively charged, allowing them to interact with negatively charged DNA, helping to compact it into a condensed form called chromatin.

Key Definitions