A Unity and Diversity

A1.1 Water

A1.2 Nucleic acids

A1.2.1—DNA as genetic material

A1.2.2—Components of a nucleotide

A1.2.3—Sugar-phosphate bonding

A1.2.4—Bases form the basis of a code

A1.2.5—RNA as a polymer

A1.2.6—DNA as a double helix

A1.2.7—Differences between DNA and RNA

A1.2.8—Complementary base pairing

A1.2.9—Diversity of DNA base sequences

A1.2.10—Conservation of genetic code

A1.2.11 (HL)—Directionality of RNA and DNA

A1.2.12 (HL)—Purine-to-pyrimidine bonding and helix stability

A1.2.13 (HL)—Structure of a nucleosome

A1.2.14 (HL)—Hershey-Chase experiment

A1.2.15 (HL)—Chargaff's data

A2.1 Origins of cells

A2.2 Cell structure

A2.3 Viruses [HL only]

A3.1 Diversity of organisms

A3.2 Classification and cladistics [HL only]

A4.1 Evolution and speciation

A4.2 Conservation of biodiversity

B Form and Function

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 only]

B4.1 Adaptation to environment

B4.2 Ecological niches

C Interaction and Interdependence

C1.1 Enzymes and metabolism

C1.2 Cell respiration

C1.3 Photosynthesis

C2.1 Chemical signalling [HL only]

C2.2 Neural signalling

C3.1 Integration of body systems

C3.2 Defence against disease

C4.1 Populations and communities

C4.2 Transfers of energy and matter

D Continuity and Change

D1.1 DNA replication

D1.2 Protein synthesis

D1.3 Mutation and gene editing

D2.1 Cell and nuclear division

D2.2 Gene expression [HL only]

D2.3 Water potential

D3.1 Reproduction

D3.2 Inheritance

D3.3 Homeostasis

D4.1 Natural selection

D4.2 Stability and change

D4.3 Climate change

IB Biology HL A1.2.13 (HL)—Structure of a nucleosome Question Bank

• DNA wraps nearly twice around an octamer of histone proteins

• H1 histone binds linker DNA to the histone core

• Nucleosomes package DNA and allow regulated access to genes

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