Source: https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-6-dna-profiling-and-forensics

[Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [International A Level](https://senecalearning.com/en-gb/revision-notes/international-a-level.md) › [Biology](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology.md) › [Cambridge International](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international.md) › DNA Profiling & Forensics

# DNA Profiling & Forensics

Biology: Cambridge International A Level, topic 19.2.6

## DNA Profiling

DNA profiling is a technique for analysing samples of DNA and has multiple applications from police forensics to screening for heritable disease. DNA ‘profiles’ are specific DNA patterns that can be used to identify people, families and diseases.

### DNA contains polymorphisms

![DNA contains polymorphisms](https://image-v2.cdn.app.senecalearning.com/2018-09/43f1bd30-35fa-4c15-b7f8-02d54fcd926f/dna-genes-genetics-.jpg)

- Humans share 99.9% of DNA with one another.
- Certain regions of our genomes do vary greatly, these varying regions are known as polymorphisms.
Polymorphic DNA can be used to distinguish between target individuals and groups.

### Obtaining DNA for analysis

![Obtaining DNA for analysis](https://image-v2.cdn.app.senecalearning.com/courseImages/biology/OCR%2021%20Century/2%20Health/microscope.jpg)

- DNA samples are obtained from hairs, skin, semen, saliva or any other sample that contains body cells.
- DNA is extracted from the nucleus of the cells and isolated from other cellular matter using chemicals such as detergents.

### Polymerase chain reaction

![Polymerase chain reaction](https://image-v2.cdn.app.senecalearning.com/2018-10/ba63bc49-7b9d-4251-a350-8dc6769119fe/polymerase-chain-reaction-.png)

- DNA is replicated using polymerisation chain reaction (PCR) to increase the sample size:
 - The DNA is heated to 96oC to denature the strands and provide single-stranded templates for replication.
 - The reaction is cooled to 60oC to allow primers (short lengths of DNA to which free nucleotides can attach) to anneal to the single strands of DNA.
 - The reaction is heated to 72oC so that Taq polymerase (the DNA polymerase enzyme used) can work at optimum conditions and rapidly extend the nucleotide chains from the primers.
- This process is repeated 25-35 times and the amount of DNA increases exponentially with each repeat.

### Gel electrophoresis

![Gel electrophoresis](https://image-v2.cdn.app.senecalearning.com/2018-11/10f54cd9-517f-416a-80cc-4b097085a496/PCR.png)

- Gel electrophoresis is a technique for separating the DNA fragments out according to size (number of base pairs).
- The DNA is loaded into wells at one end of a slab of agarose gel and an electric current is passed through.
- The negatively charged DNA moves through the gel towards the positive electrode, with the smaller fragments moving faster and further.
- The DNA ends up arranged in bands, with similar length strands grouping together.

### Applications of DNA profiling

![Applications of DNA profiling](https://image-v2.cdn.app.senecalearning.com/2018-09/fece07b6-bbf0-49f2-900e-8b12518d9fbf/hacker-crime-ciminal-.jpg)

- Once sequenced, and the exact series of nucleotides in the sample has been established, forensic scientists can match the sample up with samples of DNA from known sources.
- DNA profiling is used at crime scenes to identify potential criminals, to identify whether somebody is at risk of a genetic disease or simply to find out the degree of relatedness between people.

## Test yourself on DNA Profiling & Forensics

- Which enzyme used in the polymerase chain reaction works at an optimum temperature of 72oC?

[Practise this topic for free](https://app.senecalearning.com/classroom/course/8d1a05c1-df92-4b13-9a69-b60acc7af79a/section/132ce019-1ced-4b54-b14d-ebea02144a4f/session)

- Previous topic: [19.2.5 Ethics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-5-ethics.md)
- Next topic: [19.3.1 GM Crops & Livestock](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-3-1-gm-crops-and-livestock.md)

## Biology: Cambridge International A Level contents

### 1 Cell Structure
- 1.1 Cell Structure
  - [1.1.1 Studying Cells - Microscopes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-1-studying-cells-microscopes.md)
  - [1.1.2 Introduction to Eukaryotic & Prokaryotic Cells](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-2-introduction-to-eukaryotic-and-prokaryotic-cells.md)
  - [1.1.3 Ultrastructure of Eukaryotic Cells](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-3-ultrastructure-of-eukaryotic-cells.md)
  - [1.1.4 Ultrastructure of Eukaryotic Cells 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-4-ultrastructure-of-eukaryotic-cells-2.md)
  - [1.1.5 Ultrastructure of Eukaryotic Cells 3](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-5-ultrastructure-of-eukaryotic-cells-3.md)
  - [1.1.6 Prokaryotic Cells](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-6-prokaryotic-cells.md)
  - [1.1.7 Viruses](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-7-viruses.md)
  - [1.1.8 End of Topic Test - Cell Structure](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-8-end-of-topic-test-cell-structure.md)
  - [1.1.9 Exam-Style Question - Microscopes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-9-exam-style-question-microscopes.md)
  - [1.1.10 A-A* (AO2/3) - Cell Structure](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/1-1-10-a-a-ao23-cell-structure.md)

### 2 Biological Molecules
- 2.1 Testing for Biological Modules
  - [2.1.1 Tests for Sugars & Starch](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-1-1-tests-for-sugars-and-starch.md)
  - [2.1.2 Tests for Lipids & Proteins](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-1-2-tests-for-lipids-and-proteins.md)
- 2.2 Carbohydrates & Lipids
  - [2.2.1 Monomers & Polymers](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-2-1-monomers-and-polymers.md)
  - [2.2.2 Carbohydrates](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-2-2-carbohydrates.md)
  - [2.2.3 Examples of Carbohydrates](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-2-3-examples-of-carbohydrates.md)
  - [2.2.4 Triglycerides & Phospholipids](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-2-4-triglycerides-and-phospholipids.md)
  - [2.2.5 Types of Fatty Acids](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-2-5-types-of-fatty-acids.md)
  - [2.2.6 Exam-Style Question - Carbohydrates](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-2-6-exam-style-question-carbohydrates.md)
  - [2.2.7 End of Topic Test - Carbohydrates & Lipids](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-2-7-end-of-topic-test-carbohydrates-and-lipids.md)
- 2.3 Proteins
  - [2.3.1 Amino Acids & Overview of Protein Structure](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-3-1-amino-acids-and-overview-of-protein-structure.md)
  - [2.3.2 Primary & Secondary Structure](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-3-2-primary-and-secondary-structure.md)
  - [2.3.3 Tertiary & Quaternary Structure](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-3-3-tertiary-and-quaternary-structure.md)
  - [2.3.4 Globular & Fibrous Proteins](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-3-4-globular-and-fibrous-proteins.md)
  - [2.3.5 Haemoglobin](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-3-5-haemoglobin.md)
  - [2.3.6 Collagen](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-3-6-collagen.md)
  - [2.3.7 End of Topic Test  - Proteins](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-3-7-end-of-topic-test-proteins.md)
- 2.4 Water
  - [2.4.1 Water Structure & Function](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-4-1-water-structure-and-function.md)
  - [2.4.2 End of Topic Test - Water](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/2-4-2-end-of-topic-test-water.md)

### 3 Enzymes
- 3.1 Enzymes
  - [3.1.1 Enzyme Action](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/3-1-1-enzyme-action.md)
  - [3.1.2 Factors Affecting Enzyme Activity](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/3-1-2-factors-affecting-enzyme-activity.md)
  - [3.1.3 Factors Affecting Enzyme Activity 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/3-1-3-factors-affecting-enzyme-activity-2.md)
  - [3.1.4 A-A* (AO2/3) - Enzymes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/3-1-4-a-a-ao23-enzymes.md)

### 4 Cell Membranes & Transport
- 4.1 Biological Membranes
  - [4.1.1 Fluid Mosaic Model](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-1-1-fluid-mosaic-model.md)
  - [4.1.2 Cell Signalling](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-1-2-cell-signalling.md)
  - [4.1.3 End of Topic Test - Biological Membranes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-1-3-end-of-topic-test-biological-membranes.md)
  - [4.1.4 Exam-Style Question - Membranes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-1-4-exam-style-question-membranes.md)
- 4.2 Movement Into & Out of Cells
  - [4.2.1 Passive Movement Across the Membrane](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-1-passive-movement-across-the-membrane.md)
  - [4.2.2 Active Movement Across the Membrane](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-2-active-movement-across-the-membrane.md)
  - [4.2.3 Osmosis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-3-osmosis.md)
  - [4.2.4 Osmosis & Plant Cells](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-4-osmosis-and-plant-cells.md)
  - [4.2.5 Surface Area to Volume Ratio](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-5-surface-area-to-volume-ratio.md)
  - [4.2.6 Adaptions to Surface Area to Volume Ratio](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-6-adaptions-to-surface-area-to-volume-ratio.md)
  - [4.2.7 Calculations - Volume](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-7-calculations-volume.md)
  - [4.2.8 Calculations - Surface Area](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/4-2-8-calculations-surface-area.md)

### 5 The Mitotic Cell Cycle
- 5.1 Replication & Division of Nuclei
  - [5.1.1 Chromosomes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-1-chromosomes.md)
  - [5.1.2 The Cell Cycle](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-2-the-cell-cycle.md)
  - [5.1.3 Mitosis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-3-mitosis.md)
  - [5.1.4 Role of Mitosis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-4-role-of-mitosis.md)
  - [5.1.5 Stem Cells](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-5-stem-cells.md)
  - [5.1.6 Mitosis & Cancer](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-6-mitosis-and-cancer.md)
  - [5.1.7 End of Topic Test - Replication & Division](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-7-end-of-topic-test-replication-and-division.md)
  - [5.1.8 A-A* (AO2/3) - Cell Cycle & Transport](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/5-1-8-a-a-ao23-cell-cycle-and-transport.md)

### 6 Nucleic Acids & Protein Synthesis
- 6.1 Nucleic Acids
  - [6.1.1 Introduction to DNA & RNA](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-1-introduction-to-dna-and-rna.md)
  - [6.1.2 Nucleotides](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-2-nucleotides.md)
  - [6.1.3 Polynucleotides](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-3-polynucleotides.md)
  - [6.1.4 ADP & ATP](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-4-adp-and-atp.md)
  - [6.1.5 DNA](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-5-dna.md)
  - [6.1.6 DNA Replication](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-6-dna-replication.md)
  - [6.1.7 RNA](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-7-rna.md)
  - [6.1.8 End of Topic Test - Nucleic Acids & ATP](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-1-8-end-of-topic-test-nucleic-acids-and-atp.md)
- 6.2 Protein Synthesis
  - [6.2.1 The Genetic Code](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-2-1-the-genetic-code.md)
  - [6.2.2 Polypeptide Synthesis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-2-2-polypeptide-synthesis.md)
  - [6.2.3 RNA Processing in Eukaryotes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-2-3-rna-processing-in-eukaryotes.md)
  - [6.2.4 Mutations](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-2-4-mutations.md)
  - [6.2.5 Exam-Style Question - Protein Synthesis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-2-5-exam-style-question-protein-synthesis.md)
  - [6.2.6 A-A* (AO2/3) - Coronavirus Translation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/6-2-6-a-a-ao23-coronavirus-translation.md)

### 7 Transport in Plants
- 7.1 Transport in Plants
  - [7.1.1 Plant Vessels](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/7-1-1-plant-vessels.md)
  - [7.1.2 Xylem](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/7-1-2-xylem.md)
  - [7.1.3 Investigating Transpiration](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/7-1-3-investigating-transpiration.md)
  - [7.1.4 Adaptations to Water Availability](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/7-1-4-adaptations-to-water-availability.md)
  - [7.1.5 Phloem](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/7-1-5-phloem.md)
  - [7.1.6 End of Topic Test - Transport in Animals & Plants](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/7-1-6-end-of-topic-test-transport-in-animals-and-plants.md)
  - [7.1.7 A-A* (AO2/3) - Transport in Animals & Plants](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/7-1-7-a-a-ao23-transport-in-animals-and-plants.md)

### 8 Transport in Mammals
- 8.1 Circulatory System
  - [8.1.1 Double Circulation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-1-1-double-circulation.md)
  - [8.1.2 Blood Vessels](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-1-2-blood-vessels.md)
  - [8.1.3 Important Blood Vessels](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-1-3-important-blood-vessels.md)
  - [8.1.4 Blood Cells](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-1-4-blood-cells.md)
  - [8.1.5 Tissue Fluid](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-1-5-tissue-fluid.md)
- 8.2 Transport of Oxygen & Carbon Dioxide
  - [8.2.1 Haemoglobin](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-2-1-haemoglobin.md)
  - [8.2.2 Oxygen Dissociation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-2-2-oxygen-dissociation.md)
- 8.3 The Heart
  - [8.3.1 Structure of the Heart](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-3-1-structure-of-the-heart.md)
  - [8.3.2 The Cardiac Cycle](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-3-2-the-cardiac-cycle.md)
  - [8.3.3 Coordination of Heart Action](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/8-3-3-coordination-of-heart-action.md)

### 9 Gas Exchange
- 9.1 Gas Exchange System
  - [9.1.1 Mammalian Gas Exchange](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/9-1-1-mammalian-gas-exchange.md)
  - [9.1.2 Smoking](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/9-1-2-smoking.md)

### 10 Infectious Diseases
- 10.1 Infectious Diseases
  - [10.1.1 Transmission of Disease](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/10-1-1-transmission-of-disease.md)
  - [10.1.2 Tuberculosis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/10-1-2-tuberculosis.md)
  - [10.1.3 HIV](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/10-1-3-hiv.md)
  - [10.1.4 Malaria](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/10-1-4-malaria.md)
  - [10.1.5 Cholera](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/10-1-5-cholera.md)
  - [10.1.6 Measles](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/10-1-6-measles.md)
- 10.2 Antibiotics
  - [10.2.1 Antibiotics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/10-2-1-antibiotics.md)

### 11 Immunity
- 11.1 The Immune System
  - [11.1.1 Phagocytes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-1-1-phagocytes.md)
  - [11.1.2 Antigens](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-1-2-antigens.md)
  - [11.1.3 Lymphocytes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-1-3-lymphocytes.md)
  - [11.1.4 Primary & Secondary Response](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-1-4-primary-and-secondary-response.md)
- 11.2 Antibodies & Vaccination
  - [11.2.1 Antibodies](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-2-1-antibodies.md)
  - [11.2.2 Monoclonal Antibodies](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-2-2-monoclonal-antibodies.md)
  - [11.2.3 Immunity](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-2-3-immunity.md)
  - [11.2.4 Vaccines](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-2-4-vaccines.md)
  - [11.2.5 Exam-Style Question - Immune System](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-2-5-exam-style-question-immune-system.md)
  - [11.2.6 A-A* (AO2/3) - Disease & Immune System](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/11-2-6-a-a-ao23-disease-and-immune-system.md)

### 12 Energy & Respiration (A2 Only)
- 12.1 Energy
  - [12.1.1 Energy & ATP](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-1-1-energy-and-atp.md)
  - [12.1.2 Respiratory Substrates & Quotient](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-1-2-respiratory-substrates-and-quotient.md)
  - [12.1.3 Respirometers](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-1-3-respirometers.md)
- 12.2 Respiration
  - [12.2.1 Introduction to Respiration](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-1-introduction-to-respiration.md)
  - [12.2.2 Anaerobic Respiration](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-2-anaerobic-respiration.md)
  - [12.2.3 Aerobic Respiration](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-3-aerobic-respiration.md)
  - [12.2.4 Chemiosmosis & Coenzymes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-4-chemiosmosis-and-coenzymes.md)
  - [12.2.5 Mitochondria](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-5-mitochondria.md)
  - [12.2.6 Respiration Experiments](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-6-respiration-experiments.md)
  - [12.2.7 End of Topic Test - Respiration](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-7-end-of-topic-test-respiration.md)
  - [12.2.8 A-A* (AO3/4) - Respiration](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/12-2-8-a-a-ao34-respiration.md)

### 13 Photosynthesis (A2 Only)
- 13.1 Photosynthesis
  - [13.1.1 Introduction to Photosynthesis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/13-1-1-introduction-to-photosynthesis.md)
  - [13.1.2 Light-Dependent Reactions](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/13-1-2-light-dependent-reactions.md)
  - [13.1.3 Light-Independent Reactions](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/13-1-3-light-independent-reactions.md)
  - [13.1.4 Limiting Factors](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/13-1-4-limiting-factors.md)
  - [13.1.5 Investigating Photosynthesis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/13-1-5-investigating-photosynthesis.md)
  - [13.1.6 End of Topic Test - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/13-1-6-end-of-topic-test-photosynthesis.md)
  - [13.1.7 A-A* (AO3/4) - Photosynthesis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/13-1-7-a-a-ao34-photosynthesis.md)

### 14 Homeostasis (A2 Only)
- 14.1 Homeostasis
  - [14.1.1 Homeostasis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-1-1-homeostasis.md)
  - [14.1.2 Negative Feedback](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-1-2-negative-feedback.md)
- 14.2 The Kidney
  - [14.2.1 Kidneys & Osmoregulation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-2-1-kidneys-and-osmoregulation.md)
- 14.3 Cell Signalling
  - [14.3.1 Messengers & cAMP](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-3-1-messengers-and-camp.md)
- 14.4 Blood Glucose Concentration
  - [14.4.1 Blood Glucose Concentration](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-4-1-blood-glucose-concentration.md)
  - [14.4.2 Controlling Blood Glucose](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-4-2-controlling-blood-glucose.md)
  - [14.4.3 Urinalysis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-4-3-urinalysis.md)
- 14.5 Homeostasis in Plants
  - [14.5.1 Stomata & Guard Cells](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/14-5-1-stomata-and-guard-cells.md)

### 15 Control & Coordination (A2 Only)
- 15.1 Control & Coordination in Mammals
  - [15.1.1 Neurones](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-1-neurones.md)
  - [15.1.2 Receptors](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-2-receptors.md)
  - [15.1.3 Taste](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-3-taste.md)
  - [15.1.4 Reflexes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-4-reflexes.md)
  - [15.1.5 Action Potentials](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-5-action-potentials.md)
  - [15.1.6 Saltatory Conduction](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-6-saltatory-conduction.md)
  - [15.1.7 Synapses](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-7-synapses.md)
  - [15.1.8 Cholinergic Synnapses](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-8-cholinergic-synnapses.md)
  - [15.1.9 Neuromuscular Junction](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-9-neuromuscular-junction.md)
  - [15.1.10 Skeletal Muscle](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-10-skeletal-muscle.md)
  - [15.1.11 Sliding Filament Theory Contraction](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-11-sliding-filament-theory-contraction.md)
  - [15.1.12 Sliding Filament Theory Contraction 2](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-12-sliding-filament-theory-contraction-2.md)
  - [15.1.13 Menstruation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-13-menstruation.md)
  - [15.1.14 Contraceptive Pill](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-1-14-contraceptive-pill.md)
- 15.2 Control & Co-Ordination in Plants
  - [15.2.1 Venus Flytrap](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-2-1-venus-flytrap.md)
  - [15.2.2 Auixns](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-2-2-auixns.md)
  - [15.2.3 Gibberellins](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/15-2-3-gibberellins.md)

### 16 Inherited Change (A2 Only)
- 16.1 Passage of Information to Offspring
  - [16.1.1 Meiosis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-1-1-meiosis.md)
  - [16.1.2 Gametogenesis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-1-2-gametogenesis.md)
  - [16.1.3 Meiosis & Genetic Diversity](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-1-3-meiosis-and-genetic-diversity.md)
- 16.2 Genes & Phenotype
  - [16.2.1 Key Terms in Genetics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-1-key-terms-in-genetics.md)
  - [16.2.2 Inheritance](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-2-inheritance.md)
  - [16.2.3 Linkage](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-3-linkage.md)
  - [16.2.4 Multiple Alleles](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-4-multiple-alleles.md)
  - [16.2.5 Chi-Squared Test](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-5-chi-squared-test.md)
  - [16.2.6 Mutations](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-6-mutations.md)
  - [16.2.7 Specific Mutations](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-7-specific-mutations.md)
  - [16.2.8 End of Topic Test - Genetics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-8-end-of-topic-test-genetics.md)
  - [16.2.9 A-A* (AO2/3) - Genetics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-2-9-a-a-ao23-genetics.md)
- 16.3 Gene Control
  - [16.3.1 lac Operon](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-3-1-lac-operon.md)
  - [16.3.2 Transcription Factors](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-3-2-transcription-factors.md)
  - [16.3.3 Gibberellins & DELLA Proteins](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/16-3-3-gibberellins-and-della-proteins.md)

### 17 Selection & Evolution (A2 Only)
- 17.1 Variation
  - [17.1.1 Phenotypic Variation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-1-1-phenotypic-variation.md)
  - [17.1.2 Continuous & Discontinuous Variation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-1-2-continuous-and-discontinuous-variation.md)
  - [17.1.3 t-Tests](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-1-3-t-tests.md)
- 17.2 Natural & Artificial Selection
  - [17.2.1 Natural Selection & Evolution](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-2-1-natural-selection-and-evolution.md)
  - [17.2.2 Types of Selection](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-2-2-types-of-selection.md)
  - [17.2.3 Types of Selection Summary](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-2-3-types-of-selection-summary.md)
  - [17.2.4 Genetic Drift & Founder Effect](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-2-4-genetic-drift-and-founder-effect.md)
  - [17.2.5 Populations](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-2-5-populations.md)
  - [17.2.6 Hardy-Weinberg Principle](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-2-6-hardy-weinberg-principle.md)
  - [17.2.7 Artificial Selection](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-2-7-artificial-selection.md)
- 17.3 Evolution
  - [17.3.1 Evolution by Natural Selection](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-3-1-evolution-by-natural-selection.md)
  - [17.3.2 Evidence for Evolution](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-3-2-evidence-for-evolution.md)
  - [17.3.3 Speciation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-3-3-speciation.md)
  - [17.3.4 Extinction](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/17-3-4-extinction.md)

### 18 Classification & Conservation (A2 Only)
- 18.1 Biodiversity
  - [18.1.1 Key Terms](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-1-1-key-terms.md)
  - [18.1.2 Biodiversity](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-1-2-biodiversity.md)
  - [18.1.3 Sampling Methods](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-1-3-sampling-methods.md)
  - [18.1.4 Correlation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-1-4-correlation.md)
  - [18.1.5 Spearman’s Rank](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-1-5-spearmans-rank.md)
  - [18.1.6 Measuring Biodiversity](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-1-6-measuring-biodiversity.md)
- 18.2 Classification
  - [18.2.1 3-Domain Classification System](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-2-1-3-domain-classification-system.md)
  - [18.2.2 Linnaean Classification System](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-2-2-linnaean-classification-system.md)
- 18.3 Conservation
  - [18.3.1 Importance of Biodiversity](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-3-1-importance-of-biodiversity.md)
  - [18.3.2 Conservation](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-3-2-conservation.md)
  - [18.3.3 Zoos, Seedbanks, & Other Conservation Methods](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-3-3-zoos-seedbanks-and-other-conservation-methods.md)
  - [18.3.4 Assisted Reproduction & Contraception](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-3-4-assisted-reproduction-and-contraception.md)
  - [18.3.5 Non-Governmental Organisations](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/18-3-5-non-governmental-organisations.md)

### 19 Genetic Technology (A2 Only)
- 19.1 Manipulating Genomes
  - [19.1.1 Recombinant DNA & Genetic Engineering](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-1-1-recombinant-dna-and-genetic-engineering.md)
  - [19.1.2 Restriction Endonucleases](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-1-2-restriction-endonucleases.md)
  - [19.1.3 Gel Electrophoresis](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-1-3-gel-electrophoresis.md)
  - [19.1.4 DNA Probes & Microarrays](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-1-4-dna-probes-and-microarrays.md)
  - [19.1.5 End of Topic Test - Manipulating Genomes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-1-5-end-of-topic-test-manipulating-genomes.md)
  - [19.1.6 A-A* (AO2/3) - Manipulating Genomes](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-1-6-a-a-ao23-manipulating-genomes.md)
- 19.2 Genetic Technology Applied to Medicine
  - [19.2.1 Bioinformatics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-1-bioinformatics.md)
  - [19.2.2 Applications of Recombinant DNA](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-2-applications-of-recombinant-dna.md)
  - [19.2.3 Genetic Screening](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-3-genetic-screening.md)
  - [19.2.4 Gene Therapy](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-4-gene-therapy.md)
  - [19.2.5 Ethics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-5-ethics.md)
  - [19.2.6 DNA Profiling & Forensics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-2-6-dna-profiling-and-forensics.md)
- 19.3 Genetically Modified Organisms in Agriculture
  - [19.3.1 GM Crops & Livestock](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-3-1-gm-crops-and-livestock.md)
  - [19.3.2 Ethics](https://senecalearning.com/en-gb/revision-notes/international-a-level/biology/cambridge-international/19-3-2-ethics.md)