Source: https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-1-2-chromosomal-basis-of-inherited-disorders [Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [IB Diploma](https://senecalearning.com/en-gb/revision-notes/ib-diploma.md) › [Biology](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology.md) › [Biology: IB Diploma](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma.md) › Chromosomal Basis of Inherited Disorders # Chromosomal Basis of Inherited Disorders Biology: IB Diploma Higher Level, topic 3.1.2 ## Chromosomal Basis of Inherited Disorders Inherited disorders can arise when chromosomes behave abnormally during meiosis. Chromosome disorders can be due to abnormalities in chromosome number or due to chromosomal structural rearrangements. ### Identification of chromosomes ![Identification of chromosomes](https://image-v2.cdn.app.senecalearning.com/2018-04/1c95b036-57cb-4edb-b318-33fb72112e77/shutterstock_732530512.jpg) - The isolation and microscopic observation of chromosomes forms the basis of cytogenetics and is the primary method by which clinicians detect chromosomal abnormalities in humans. - A karyotype is the number and appearance of chromosomes, and includes their length, banding pattern, and centromere position. - To obtain a view of an individual’s karyotype, cytologists photograph the chromosomes and then cut and paste each chromosome into a chart, or karyogram ### Disorders in chromosome number ![Disorders in chromosome number](https://image-v2.cdn.app.senecalearning.com/2018-09/041bd706-faf5-4279-bbb6-2c9b626f1cb4/chromosome-pair-homologous-.png) - Disorders of chromosome number include the duplication or loss of entire chromosomes, as well as changes in the number of complete sets of chromosomes. - They are caused by **nondisjunction**, which occurs when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis. - Misaligned or incomplete synapsis, or a dysfunction of the spindle apparatus, can cause nondisjunction. - The risk of nondisjunction occurring increases with the age of the parents. ### Nondisjunction ![Nondisjunction](https://image-v2.cdn.app.senecalearning.com/2020-01/392d001b-23da-4fe3-93fe-15a713c93583/non%20disjunction%20(2).png) - Nondisjunction can occur during either meiosis I or II, with differing results. - If homologous chromosomes fail to separate during meiosis I: - The result is two gametes that lack that particular chromosome and two gametes with two copies of the chromosome. - If sister chromatids fail to separate during meiosis II: - The result is one gamete that lacks that chromosome, two normal gametes with one copy of the chromosome, and one gamete with two copies of the chromosome. ### Nondisjunction ![Nondisjunction](https://image-v2.cdn.app.senecalearning.com/2020-01/392d001b-23da-4fe3-93fe-15a713c93583/non%20disjunction%20(2).png) ### Aneuploidy ![Aneuploidy](https://image-v2.cdn.app.senecalearning.com/2018-09/a9b78626-b8db-47c3-8869-aa3304737290/chromosomes-156403_1280.png) - An individual with the appropriate number of chromosomes for their species is called euploid. - In humans, euploidy corresponds to 22 pairs of autosomes and one pair of sex chromosomes. - An individual with an error in chromosome number is described as aneuploid, a term that includes: - **Monosomy**, a loss of one chromosome. - **Trisomy**, a gain of an extraneous chromosome. ### Trisomy 21 ![Trisomy 21](https://image-v2.cdn.app.senecalearning.com/2018-09/4199ed74-efa3-436b-a354-cf272498b766/medic-563425_1920.jpg) - The most common trisomy among viable births is that of chromosome 21, which corresponds to Down Syndrome. - Individuals with an extra chromosome 21 may synthesize an abundance of the gene products encoded by that chromosome. - This extra dose (150 percent) of specific genes can lead to a number of functional challenges. - Individuals with this inherited disorder are characterized by short stature and stunted digits, facial distinctions, and developmental delays. ## Test yourself on Chromosomal Basis of Inherited Disorders - When can non-disjunction occur? - What are the results of nondisjunction in meiosis I? [Practise this topic for free](https://app.senecalearning.com/classroom/course/549189f7-f13a-4c5c-b80c-ea1bd3036d78/section/639314da-e8cb-4d6d-81ad-6151e6a7b3c1/session) - Previous topic: [3.1.1 Chromosomal Theory of Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-1-1-chromosomal-theory-of-inheritance.md) - Next topic: [3.1.3 IB Multiple Choice - Chromosomal Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-1-3-ib-multiple-choice-chromosomal-inheritance.md) ## Biology: IB Diploma Higher Level contents ### 1 Unity & Diversity - Molecules - 1.1 Water - [1.1.1 The Importance of Water](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-1-1-the-importance-of-water.md) - [1.1.2 The Structure of Water](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-1-2-the-structure-of-water.md) - [1.1.3 The Properties of Water](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-1-3-the-properties-of-water.md) - [1.1.4 IB Multiple Choice - Water & Hydrogen Bonding](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-1-4-ib-multiple-choice-water-and-hydrogen-bonding.md) - [1.1.5 Extended Response - Water](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-1-5-extended-response-water.md) - 1.2 DNA Structure & Replication - [1.2.1 DNA](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-2-1-dna.md) - [1.2.2 RNA](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-2-2-rna.md) - [1.2.3 Semi-Conservative DNA Replication](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-2-3-semi-conservative-dna-replication.md) - [1.2.4 DNA Replication](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-2-4-dna-replication.md) - [1.2.5 DNA Replication - Summary](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-2-5-dna-replication-summary.md) - [1.2.6 IB Multiple Choice - DNA Replication](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-2-6-ib-multiple-choice-dna-replication.md) - 1.3 Transcription & Gene Expression - [1.3.1 Introduction to Transcription & Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-3-1-introduction-to-transcription-and-protein-synthesis.md) - [1.3.2 Types of RNA](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-3-2-types-of-rna.md) - [1.3.3 Transcription](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-3-3-transcription.md) - [1.3.4 RNA Processing in Eukaryotes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-3-4-rna-processing-in-eukaryotes.md) - [1.3.5 IB Multiple Choice - Transcription](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-3-5-ib-multiple-choice-transcription.md) - 1.4 Translation - [1.4.1 Translation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-4-1-translation.md) - [1.4.2 Retroviruses](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-4-2-retroviruses.md) - [1.4.3 Scientific Practices: Coronavirus](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-4-3-scientific-practices-coronavirus.md) - [1.4.4 IB Multiple Choice - Translation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/1-4-4-ib-multiple-choice-translation.md) ### 2 Unity & Diversity - Cells - 2.1 The Origin of Cells - [2.1.1 Origins - Endosymbiosis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-1-1-origins-endosymbiosis.md) - 2.2 Introduction to Cells - [2.2.1 Introduction to Cells](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-2-1-introduction-to-cells.md) - [2.2.2 Cell Size & Surface Area](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-2-2-cell-size-and-surface-area.md) - [2.2.3 Surface Area to Volume Ratio](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-2-3-surface-area-to-volume-ratio.md) - [2.2.4 Eukaryotic vs Prokaryotic Cells](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-2-4-eukaryotic-vs-prokaryotic-cells.md) - [2.2.5 Stem Cells](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-2-5-stem-cells.md) - [2.2.6 Stem Cells in Disease](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-2-6-stem-cells-in-disease.md) - 2.3 Ultrastructure of Cells - [2.3.1 Golgi, Lysosomes & Ribosomes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-3-1-golgi-lysosomes-and-ribosomes.md) - [2.3.2 Cell Walls & Vacuole](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-3-2-cell-walls-and-vacuole.md) - [2.3.3 Prokaryotes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-3-3-prokaryotes.md) - [2.3.4 Binary Fission](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-3-4-binary-fission.md) - 2.4 Cell Division - [2.4.1 The Cell Cycle](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-4-1-the-cell-cycle.md) - [2.4.2 Mitosis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-4-2-mitosis.md) - [2.4.3 Regulation of the Cell Cycle](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-4-3-regulation-of-the-cell-cycle.md) - [2.4.4 End of Topic Quiz - The Cell Cycle](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-4-4-end-of-topic-quiz-the-cell-cycle.md) - [2.4.5 IB Multiple Choice - The Cell Cycle](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-4-5-ib-multiple-choice-the-cell-cycle.md) - [2.4.6 Extended Response - Mitosis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-4-6-extended-response-mitosis.md) - 2.5 Structure of DNA & RNA - [2.5.1 DNA & RNA](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-5-1-dna-and-rna.md) - 2.6 DNA Replication, Transcription & Translation - [2.6.1 Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-6-1-protein-synthesis.md) - [2.6.2 Transcription & Translation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-6-2-transcription-and-translation.md) - [2.6.3 End of Topic Test - DNA, Genes & Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-6-3-end-of-topic-test-dna-genes-and-protein-synthesis.md) - [2.6.4 Exam-Style Question - Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-6-4-exam-style-question-protein-synthesis.md) - [2.6.5 End of Topic Test - Coronavirus Translation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-6-5-end-of-topic-test-coronavirus-translation.md) - [2.6.6 IB Multiple Choice - Transcription](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-6-6-ib-multiple-choice-transcription.md) - [2.6.7 IB Multiple Choice - Translation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-6-7-ib-multiple-choice-translation.md) - 2.7 Cell Respiration - [2.7.1 Overview of Respiration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-7-1-overview-of-respiration.md) - [2.7.2 Anaerobic Respiration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-7-2-anaerobic-respiration.md) - [2.7.3 End of Topic Test - Anaerobic Respiration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-7-3-end-of-topic-test-anaerobic-respiration.md) - [2.7.4 Respiration Experiments](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-7-4-respiration-experiments.md) - [2.7.5 End of Topic Test - Respiration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-7-5-end-of-topic-test-respiration.md) - [2.7.6 IB Multiple Choice - Respiration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-7-6-ib-multiple-choice-respiration.md) - 2.8 Photosynthesis - [2.8.1 Overview of Photosynthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-8-1-overview-of-photosynthesis.md) - 2.9 Viruses - [2.9.1 Viruses](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/2-9-1-viruses.md) ### 3 Unity & Diversity - Organisms - 3.1 Diversity of Organisms - [3.1.1 Chromosomal Theory of Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-1-1-chromosomal-theory-of-inheritance.md) - [3.1.2 Chromosomal Basis of Inherited Disorders](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-1-2-chromosomal-basis-of-inherited-disorders.md) - [3.1.3 IB Multiple Choice - Chromosomal Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-1-3-ib-multiple-choice-chromosomal-inheritance.md) - 3.2 Evidence for Evolution - [3.2.1 Evidence for Evolution - Fossils & DNA](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-2-1-evidence-for-evolution-fossils-and-dna.md) - [3.2.2 Evidence for Evolution - Anatomy & Geography](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-2-2-evidence-for-evolution-anatomy-and-geography.md) - [3.2.3 IB Multiple Choice - Evidence for Evolution](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-2-3-ib-multiple-choice-evidence-for-evolution.md) - [3.2.4 Extended Response - DNA & Evolution](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-2-4-extended-response-dna-and-evolution.md) - 3.3 Natural Selection - [3.3.1 Introduction](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-3-1-introduction.md) - [3.3.2 Evolutionary Fitness](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-3-2-evolutionary-fitness.md) - [3.3.3 Natural Selection & Variation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-3-3-natural-selection-and-variation.md) - [3.3.4 End of Topic Quiz - Natural Selection](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-3-4-end-of-topic-quiz-natural-selection.md) - [3.3.5 IB Multiple Choice - Natural Selection](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-3-5-ib-multiple-choice-natural-selection.md) - [3.3.6 Speciation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/3-3-6-speciation.md) ### 4 Unity & Diversity - Ecosystems - 4.1 Classification - [4.1.1 Introduction to Biodiversity](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-1-1-introduction-to-biodiversity.md) - [4.1.2 Keystone Species](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-1-2-keystone-species.md) - [4.1.3 Courtship & Ancestry](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-1-3-courtship-and-ancestry.md) - [4.1.4 Classification](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-1-4-classification.md) - 4.2 Cladistics - [4.2.1 Evolutionary Relationships](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-2-1-evolutionary-relationships.md) - [4.2.2 IB Multiple Choice - Species & Taxonomy](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-2-2-ib-multiple-choice-species-and-taxonomy.md) - 4.3 Evolution & Speciation - [4.3.1 Evidence for Evolution - Fossils & DNA](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-1-evidence-for-evolution-fossils-and-dna.md) - [4.3.2 Evidence for Evolution - Anatomy & Geography](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-2-evidence-for-evolution-anatomy-and-geography.md) - [4.3.3 IB Multiple Choice - Evidence for Evolution](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-3-ib-multiple-choice-evidence-for-evolution.md) - [4.3.4 Extended Response - DNA & Evolution](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-4-extended-response-dna-and-evolution.md) - [4.3.5 Populations](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-5-populations.md) - [4.3.6 Mutations, Genetic Drift, & Gene Flow](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-6-mutations-genetic-drift-and-gene-flow.md) - [4.3.7 Speciation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-7-speciation.md) - [4.3.8 Rate of Speciation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-8-rate-of-speciation.md) - [4.3.9 Allopatric & Sympatric Speciation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-3-9-allopatric-and-sympatric-speciation.md) - 4.4 Conservation of Biodiversity - [4.4.1 Coming Soon!](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/4-4-1-coming-soon.md) ### 5 Form & Function - Molecules - 5.1 Carbohydrates & Lipids - [5.1.1 Monosaccharides](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/5-1-1-monosaccharides.md) - [5.1.2 Disaccharides & Polysaccharides](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/5-1-2-disaccharides-and-polysaccharides.md) - [5.1.3 Triglycerides & Phospholipids](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/5-1-3-triglycerides-and-phospholipids.md) - [5.1.4 Cellulose](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/5-1-4-cellulose.md) - [5.1.5 Starch & Glycogen](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/5-1-5-starch-and-glycogen.md) - 5.2 Proteins - [5.2.1 Structure & Functions of Proteins](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/5-2-1-structure-and-functions-of-proteins.md) ### 6 Form & Function - Cells - 6.1 Membranes & Membrane Transport - [6.1.1 Passive Movement Across Membranes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/6-1-1-passive-movement-across-membranes.md) - [6.1.2 Active Movement Across Membranes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/6-1-2-active-movement-across-membranes.md) - [6.1.3 Endocytosis & Exocystosis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/6-1-3-endocytosis-and-exocystosis.md) - [6.1.4 Cell Membrane Structure & Permeability](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/6-1-4-cell-membrane-structure-and-permeability.md) - 6.2 Organelles & Compartmentalization - [6.2.1 Eukaryotic Cells & Organelles](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/6-2-1-eukaryotic-cells-and-organelles.md) - [6.2.2 Subcellular Components & Organelles](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/6-2-2-subcellular-components-and-organelles.md) - 6.3 Cell Specialization - [6.3.1 Cell Specialization](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/6-3-1-cell-specialization.md) ### 7 Form & Function - Organisms - 7.1 Gas Exchange - [7.1.1 Lung Structure & Alveoli](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-1-1-lung-structure-and-alveoli.md) - [7.1.2 Ventilation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-1-2-ventilation.md) - [7.1.3 Lung Disease](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-1-3-lung-disease.md) - [7.1.4 Lung Disease Data](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-1-4-lung-disease-data.md) - 7.2 Transport - [7.2.1 The Circulatory System](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-1-the-circulatory-system.md) - [7.2.2 The Heart](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-2-the-heart.md) - [7.2.3 Blood Vessels](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-3-blood-vessels.md) - [7.2.4 Cardiovascular Disease](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-4-cardiovascular-disease.md) - [7.2.5 Xylem Structure](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-5-xylem-structure.md) - [7.2.6 Cohesion-Tension Theory](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-6-cohesion-tension-theory.md) - [7.2.7 Investigating Transpiration Rate](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-7-investigating-transpiration-rate.md) - [7.2.8 Phloem Structure](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-8-phloem-structure.md) - [7.2.9 Translocation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-2-9-translocation.md) - 7.3 Muscle & Motility - [7.3.1 Skeletal Muscle](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-3-1-skeletal-muscle.md) - [7.3.2 Sliding Filament Theory](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-3-2-sliding-filament-theory.md) - [7.3.3 Contraction](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/7-3-3-contraction.md) ### 8 Form & Function - Ecosystems - 8.1 Species, Communities & Ecosytems - [8.1.1 Population Dynamics](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-1-population-dynamics.md) - [8.1.2 Communities & Measuring Diversity](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-2-communities-and-measuring-diversity.md) - [8.1.3 Relationships Between Populations](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-3-relationships-between-populations.md) - [8.1.4 Overview of Ecosystems](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-4-overview-of-ecosystems.md) - [8.1.5 Nutrient Cycles](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-5-nutrient-cycles.md) - [8.1.6 Fertilisers](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-6-fertilisers.md) - [8.1.7 Eutrophication](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-7-eutrophication.md) - [8.1.8 Chi-Squared Test](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-1-8-chi-squared-test.md) - 8.2 Energy Flow - [8.2.1 Energy](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-2-1-energy.md) - [8.2.2 Energy Flow](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-2-2-energy-flow.md) - [8.2.3 Biomass & Food Chains](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-2-3-biomass-and-food-chains.md) - [8.2.4 Heterotrophs & Autotrophs](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-2-4-heterotrophs-and-autotrophs.md) - 8.3 Carbon Cycle - [8.3.1 Carbon Cycle](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-3-1-carbon-cycle.md) - 8.4 Climate Change - [8.4.1 Carbon Dioxide](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-4-1-carbon-dioxide.md) - [8.4.2 The Greenhouse Effect](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-4-2-the-greenhouse-effect.md) - [8.4.3 Global Warming](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-4-3-global-warming.md) - [8.4.4 Maintaining Biodiversity](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/8-4-4-maintaining-biodiversity.md) ### 9 Interaction & Interdependence - Molecules - 9.1 Enzymes - [9.1.1 Enzymes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-1-1-enzymes.md) - [9.1.2 Factors Affecting Enzyme Activity](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-1-2-factors-affecting-enzyme-activity.md) - [9.1.3 Enzyme-Controlled Reactions](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-1-3-enzyme-controlled-reactions.md) - [9.1.4 End of Topic Test - Enzymes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-1-4-end-of-topic-test-enzymes.md) - 9.2 Metabolism - [9.2.1 Molecules to Metabolism](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-2-1-molecules-to-metabolism.md) - 9.3 Cell Respiration - [9.3.1 Glycolysis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-3-1-glycolysis.md) - [9.3.2 Aerobic Respiration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-3-2-aerobic-respiration.md) - 9.4 Photosynthesis - [9.4.1 Light-Dependent Reaction](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-4-1-light-dependent-reaction.md) - [9.4.2 Light-Independent Reaction](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-4-2-light-independent-reaction.md) - [9.4.3 End of Topic Test - Photosynthesis Reactions](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-4-3-end-of-topic-test-photosynthesis-reactions.md) - [9.4.4 Limiting Factors](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-4-4-limiting-factors.md) - [9.4.5 Photosynthesis Experiments](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-4-5-photosynthesis-experiments.md) - [9.4.6 End of Topic Test - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-4-6-end-of-topic-test-photosynthesis.md) - [9.4.7 End of Topic Test - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/9-4-7-end-of-topic-test-photosynthesis.md) ### 10 Interaction & Interdependence - Cells - 10.1 Chemical Signalling - [10.1.1 Coming Soon!](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-1-1-coming-soon.md) - 10.2 Neural Signalling - [10.2.1 Medical Application](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-1-medical-application.md) - [10.2.2 Speed of Transmission](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-2-speed-of-transmission.md) - [10.2.3 Synapses](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-3-synapses.md) - [10.2.4 End of Topic Test - Nervous Comm&Coord](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-4-end-of-topic-test-nervous-commandcoord.md) - [10.2.5 Neuron Structure](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-5-neuron-structure.md) - [10.2.6 Types of Synapse](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-6-types-of-synapse.md) - [10.2.7 End of Topic Test - Neurones & Action Potentials](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-7-end-of-topic-test-neurones-and-action-potentials.md) - [10.2.8 Transmission of an Impulse](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-8-transmission-of-an-impulse.md) - [10.2.9 End of Topic Test - Synapses](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-2-9-end-of-topic-test-synapses.md) - 10.3 Adaptation to Environment - [10.3.1 Coming Soon!](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-3-1-coming-soon.md) - 10.4 Ecological Niches - [10.4.1 Coming Soon!](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/10-4-1-coming-soon.md) ### 11 Interaction & Interdependence - Organisms - 11.1 Integration of Body Systems - [11.1.1 Plant Tropisms](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-1-1-plant-tropisms.md) - 11.2 Defence Against Disease - [11.2.1 Immune System](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-2-1-immune-system.md) - [11.2.2 The Immune Response](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-2-2-the-immune-response.md) - [11.2.3 Antibodies](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-2-3-antibodies.md) - [11.2.4 Primary & Secondary Response](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-2-4-primary-and-secondary-response.md) - [11.2.5 Vaccines](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-2-5-vaccines.md) - [11.2.6 HIV](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-2-6-hiv.md) - [11.2.7 End of Topic Test - Immune System](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/11-2-7-end-of-topic-test-immune-system.md) ### 12 Interaction & Interdependence - Ecosystems - 12.1 Populations & Communities - [12.1.1 Coming Soon!](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/12-1-1-coming-soon.md) - 12.2 Transfers of Energy & Matter - [12.2.1 Coming Soon!](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/12-2-1-coming-soon.md) ### 13 Continuity & Change - Molecules - 13.1 DNA Replication - [13.1.1 DNA Replication](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-1-1-dna-replication.md) - 13.2 Protein Synthesis - [13.2.1 Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-2-1-protein-synthesis.md) - [13.2.2 Transcription & Translation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-2-2-transcription-and-translation.md) - [13.2.3 End of Topic Test - DNA, Genes & Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-2-3-end-of-topic-test-dna-genes-and-protein-synthesis.md) - 13.3 Mutation & Gene Editing - [13.3.1 Genes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-3-1-genes.md) - [13.3.2 Mutations](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-3-2-mutations.md) - [13.3.3 DNA Technology](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-3-3-dna-technology.md) - [13.3.4 PCR & Gel Electrophoresis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-3-4-pcr-and-gel-electrophoresis.md) - [13.3.5 Genetic Modification](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-3-5-genetic-modification.md) - [13.3.6 Cloning](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/13-3-6-cloning.md) ### 14 Continuity & Change - Cells - 14.1 Gene Expression - [14.1.1 Introduction to Transcription & Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/14-1-1-introduction-to-transcription-and-protein-synthesis.md) - [14.1.2 Types of RNA](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/14-1-2-types-of-rna.md) - [14.1.3 Transcription](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/14-1-3-transcription.md) - [14.1.4 RNA Processing in Eukaryotes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/14-1-4-rna-processing-in-eukaryotes.md) - [14.1.5 IB Multiple Choice - Transcription](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/14-1-5-ib-multiple-choice-transcription.md) - 14.2 Water Potential - [14.2.1 Controlling Blood Water Potential](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/14-2-1-controlling-blood-water-potential.md) ### 15 Continuity & Change - Organisms - 15.1 Inheritance - [15.1.1 Non-Nuclear Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-1-non-nuclear-inheritance.md) - [15.1.2 Linked Genes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-2-linked-genes.md) - [15.1.3 IB Multiple Choice - Non-Mendelian Genetics](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-3-ib-multiple-choice-non-mendelian-genetics.md) - [15.1.4 Extended Response - Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-4-extended-response-inheritance.md) - [15.1.5 Introduction to Non-Mendelian Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-5-introduction-to-non-mendelian-inheritance.md) - [15.1.6 Chi-Squared Test](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-6-chi-squared-test.md) - [15.1.7 End of Topic Quiz - Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-7-end-of-topic-quiz-inheritance.md) - [15.1.8 Sex-Linked Genes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-8-sex-linked-genes.md) - [15.1.9 Grade 4-5 (Scientific Practices) - Inheritance](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-1-9-grade-4-5-scientific-practices-inheritance.md) - 15.2 Homeostasis - [15.2.1 Overview of Homeostasis](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-1-overview-of-homeostasis.md) - [15.2.2 Blood Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-2-blood-glucose-concentration.md) - [15.2.3 Controlling Blood Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-3-controlling-blood-glucose-concentration.md) - [15.2.4 End of Topic Test - Blood Glucose](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-4-end-of-topic-test-blood-glucose.md) - [15.2.5 Type I & Type II Diabetes](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-5-type-i-and-type-ii-diabetes.md) - [15.2.6 Human Reproductive Systems](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-6-human-reproductive-systems.md) - [15.2.7 Hormonal Control of the Menstrual Cycle](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-7-hormonal-control-of-the-menstrual-cycle.md) - [15.2.8 Kidneys & Osmoregulation](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/15-2-8-kidneys-and-osmoregulation.md) ### 16 Continuity & Change - Ecosystems - 16.1 Natural Selection - [16.1.1 Natural Selection](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/16-1-1-natural-selection.md) - 16.2 Stability & Change - [16.2.1 Coming Soon!](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/16-2-1-coming-soon.md) - 16.3 Climate Change - [16.3.1 Carbon Dioxide](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/16-3-1-carbon-dioxide.md) - [16.3.2 The Greenhouse Effect](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/16-3-2-the-greenhouse-effect.md) - [16.3.3 Global Warming](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/16-3-3-global-warming.md) - [16.3.4 Maintaining Biodiversity](https://senecalearning.com/en-gb/revision-notes/ib-diploma/biology/biology-ib-diploma/16-3-4-maintaining-biodiversity.md)