8.1.2

Effects of Mutations

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Effects of Mutation

The sequence of bases in DNA encodes the amino acids that are used in protein synthesis. If this sequence is altered by mutation, this could influence the proteins an organism produces.

Illustrative background for Encoding amino acidsIllustrative background for Encoding amino acids ?? "content

Encoding amino acids

  • There are four different bases in DNA (A, T, C, G).
  • Three bases in a sequence encode an amino acid. This is called the triplet code or a codon.
  • Every codon encodes a different amino acid.
  • Amino acids are joined together to form proteins.
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Protein 3D structure

  • Every amino acid has a side chain (called the R group) that differs slightly.
  • The bonds that can form between the R groups of different amino acids within a protein can give rise to a complex 3D structure.
  • The 3D structure of proteins is very important for their function (e.g. the shape of an enzyme active site is determine by its amino acids).
Illustrative background for MutationsIllustrative background for Mutations ?? "content

Mutations

  • Mutations give rise to a change in the base sequence in DNA.
  • This could alter the amino acids that the DNA encodes.
    • E.g. CTG encodes leucine. If this was inverted to GTC, it would encode valine.
  • If the amino acids in a protein are changed, the 3D structure of the protein may break down.
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Effect of mutation

  • If a protein's structure is affected by a mutation, this could have harmful effects.
  • Some genetic disorders are caused by mutations in this way.
    • E.g. Cystic fibrosis is caused by a mutation that affects proteins in the epithelial cells of the respiratory system.

The Degenerate Code

Some mutations have no effect on protein structure because of the degenerate nature of DNA. This is because some amino acids are encoded by more than one base triplet code.

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Triplet codes

  • Some amino acids are encoded by more than one codon (e.g. tyrosine is encoded by TAT and TAC).
  • The fact that some amino acids correspond to multiple codons means that DNA is degenerate.
Illustrative background for MutationsIllustrative background for Mutations ?? "content

Mutations

  • The fact that DNA is degenerate means that a mutation in the base sequence does not necessarily affect the protein.
  • If one base is substituted for another base, (e.g. CAA → CAG), the mutated codon may still encode the same amino acid (e.g. both encode glutamine).

Frameshift

Sometimes a mutation can have a very large impact on the protein structure if it impacts all the base triplets downstream from the mutation. This is called a frameshift.

Illustrative background for Causes of a frameshiftIllustrative background for Causes of a frameshift ?? "content

Causes of a frameshift

  • A frameshift is caused when a base (or multiple bases) is inserted, removed or duplicated into the genome.
  • This type of mutation has altered the number of bases in the DNA sequence.
  • This means that all the triplet codes downstream from the mutation will experience a shift.
Illustrative background for Effects of a frameshiftIllustrative background for Effects of a frameshift ?? "content

Effects of a frameshift

  • A frameshift causes all amino acids that follow the mutation to be affected.
  • If only one amino acid in a protein is changed in a mutation, the protein may be able to function as normal.
  • A frameshift impacts many amino acids so it is much less likely that the protein will function as normal.
Illustrative background for E.g. Crohn's diseaseIllustrative background for E.g. Crohn's disease ?? "content

E.g. Crohn's disease

  • Crohn's disease is an inflammatory bowel disease that is caused by a frameshift mutation.
  • When Cytosine is inserted at position 3020 of the NOD2 gene, the subsequent codons are shifted.
  • This causes the protein to be shortened and it cannot function properly.

Jump to other topics

1Biological Molecules

1.1Monomers & Polymers

1.1.1Monomers & Polymers

1.1.2Condensation & Hydrolysis Reactions

1.2Carbohydrates

1.2.1Structure of Carbohydrates

1.2.2Types of Polysaccharides

1.2.3End of Topic Test - Monomers, Polymers and Carbs

1.2.4Exam-Style Question - Carbohydrates

1.2.5A-A* (AO3/4) - Carbohydrates

1.3Lipids

1.3.1Triglycerides & Phospholipids

1.3.2Types of Fatty Acids

1.3.3Testing for Lipids

1.3.4Exam-Style Question - Fats

1.3.5A-A* (AO3/4) - Lipids

1.4Proteins

1.4.1The Peptide Chain

1.4.2Investigating Proteins

1.4.3Primary & Secondary Protein Structure

1.4.4Tertiary & Quaternary Protein Structure

1.4.5Enzymes

1.4.6Factors Affecting Enzyme Activity

1.4.7Enzyme-Controlled Reactions

1.4.8End of Topic Test - Lipids & Proteins

1.4.9A-A* (AO3/4) - Enzymes

1.4.10A-A* (AO3/4) - Proteins

1.5Nucleic Acids

1.5.1DNA & RNA

1.5.2Polynucleotides

1.5.3DNA Replication

1.5.4Exam-Style Question - Nucleic Acids

1.5.5A-A* (AO3/4) - Nucleic Acids

1.6ATP

1.6.1Structure of ATP

1.6.2End of Topic Test - Nucleic Acids & ATP

1.7Water

1.7.1Structure & Function of Water

1.7.2A-A* (AO3/4) - Water

1.8Inorganic Ions

1.8.1Inorganic Ions

1.8.2End of Topic Test - Water & Inorganic Ions

2Cells

2.1Cell Structure

2.1.1Introduction to Cells

2.1.2Eukaryotic Cells & Organelles

2.1.3Eukaryotic Cells & Organelles 2

2.1.4Prokaryotes

2.1.5A-A* (AO3/4) - Organelles

2.1.6Methods of Studying Cells

2.1.7Microscopes

2.1.8End of Topic Test - Cell Structure

2.1.9Exam-Style Question - Cells

2.1.10A-A* (AO3/4) - Cells

2.2Mitosis & Cancer

2.2.1Mitosis

2.2.2Investigating Mitosis

2.2.3Cancer

2.2.4A-A* (AO3/4) - The Cell Cycle

2.3Transport Across Cell Membrane

2.3.1Cell Membrane Structure

2.3.2A-A* (AO3/4) - Membrane Structure

2.3.3Diffusion

2.3.4Osmosis

2.3.5Active Transport

2.3.6End of Topic Test - Mitosis, Cancer & Transport

2.3.7Exam-Style Question - Membranes

2.3.8A-A* (AO3/4) - Membranes & Transport

2.3.9A-A*- Mitosis, Cancer & Transport

2.4Cell Recognition & the Immune System

2.4.1Immune System

2.4.2The Immune Response

2.4.3Antibodies

2.4.4Primary & Secondary Response

2.4.5Vaccines

2.4.6HIV

2.4.7Ethical Issues

2.4.8End of Topic Test - Immune System

2.4.9Exam-Style Question - Immune System

2.4.10A-A* (AO3/4) - Immune System

3Substance Exchange

3.1Surface Area to Volume Ratio

3.1.1Size & Surface Area

3.1.2A-A* (AO3/4) - Cell Size

3.2Gas Exchange

3.2.1Single-Celled Organisms

3.2.2Multicellular Organisms

3.2.3Control of Water Loss

3.2.4Human Gas Exchange

3.2.5Ventilation

3.2.6Dissection

3.2.7Measuring Gas Exchange

3.2.8Lung Disease

3.2.9Lung Disease Data

3.2.10End of Topic Test - Gas Exchange

3.2.11A-A* (AO3/4) - Gas Exchange

3.3Digestion & Absorption

3.3.1Overview of Digestion

3.3.2Digestion in Mammals

3.3.3Absorption

3.3.4End of Topic Test - Substance Exchange & Digestion

3.3.5A-A* (AO3/4) - Substance Ex & Digestion

3.4Mass Transport

3.4.1Haemoglobin

3.4.2Oxygen Transport

3.4.3The Circulatory System

3.4.4The Heart

3.4.5Blood Vessels

3.4.6Cardiovascular Disease

3.4.7Heart Dissection

3.4.8Xylem

3.4.9Phloem

3.4.10Investigating Plant Transport

3.4.11End of Topic Test - Mass Transport

3.4.12A-A* (AO3/4) - Mass Transport

4Genetic Information & Variation

4.1DNA, Genes & Chromosomes

4.1.1DNA

4.1.2Genes

4.1.3A-A* (AO3/4) - DNA

4.2DNA & Protein Synthesis

4.2.1Protein Synthesis

4.2.2Transcription & Translation

4.2.3End of Topic Test - DNA, Genes & Protein Synthesis

4.2.4Exam-Style Question - Protein Synthesis

4.2.5A-A* (AO3/4) - Coronavirus Translation

4.2.6A-A* (AO3/4) - Transcription

4.2.7A-A* (AO3/4) - Translation

4.3Mutations & Meiosis

4.3.1Mutations

4.3.2Meiosis

4.3.3A-A* (AO3/4) - Meiosis

4.3.4Meiosis vs Mitosis

4.3.5End of Topic Test - Mutations, Meiosis

4.3.6A-A* (AO3/4) - DNA,Genes, CellDiv & ProtSynth

4.4Genetic Diversity & Adaptation

4.4.1Genetic Diversity

4.4.2Natural Selection

4.4.3A-A* (AO3/4) - Natural Selection

4.4.4Adaptations

4.4.5Investigating Natural Selection

4.4.6End of Topic Test - Genetic Diversity & Adaptation

4.4.7A-A* (AO3/4) - Genetic Diversity & Adaptation

4.5Species & Taxonomy

4.5.1Classification

4.5.2DNA Technology

4.5.3A-A* (AO3/4) - Species & Taxonomy

4.6Biodiversity Within a Community

4.6.1Biodiversity

4.6.2Agriculture

4.6.3End of Topic Test - Species,Taxonomy& Biodiversity

4.6.4A-A* (AO3/4) - Species,Taxon&Biodiversity

4.7Investigating Diversity

4.7.1Genetic Diversity

4.7.2Quantitative Investigation

5Energy Transfers (A2 only)

5.1Photosynthesis

5.1.1Overview of Photosynthesis

5.1.2Light-Dependent Reaction

5.1.3Light-Independent Reaction

5.1.4A-A* (AO3/4) - Photosynthesis Reactions

5.1.5Limiting Factors

5.1.6Photosynthesis Experiments

5.1.7End of Topic Test - Photosynthesis

5.1.8A-A* (AO3/4) - Photosynthesis

5.2Respiration

5.2.1Overview of Respiration

5.2.2Anaerobic Respiration

5.2.3A-A* (AO3/4) - Anaerobic Respiration

5.2.4Aerobic Respiration

5.2.5Respiration Experiments

5.2.6End of Topic Test - Respiration

5.2.7A-A* (AO3/4) - Respiration

5.3Energy & Ecosystems

5.3.1Biomass

5.3.2Production & Productivity

5.3.3Agricultural Practices

5.4Nutrient Cycles

5.4.1Nitrogen Cycle

5.4.2Phosphorous Cycle

5.4.3Fertilisers & Eutrophication

5.4.4End of Topic Test - Nutrient Cycles

5.4.5A-A* (AO3/4) - Energy,Ecosystems&NutrientCycles

6Responding to Change (A2 only)

6.1Nervous Communication

6.1.1Survival

6.1.2Plant Responses

6.1.3Animal Responses

6.1.4Reflexes

6.1.5End of Topic Test - Reflexes, Responses & Survival

6.1.6Receptors

6.1.7The Human Retina

6.1.8Control of Heart Rate

6.1.9End of Topic Test - Receptors, Retina & Heart Rate

6.2Nervous Coordination

6.2.1Neurones

6.2.2Action Potentials

6.2.3Speed of Transmission

6.2.4End of Topic Test - Neurones & Action Potentials

6.2.5Synapses

6.2.6Types of Synapse

6.2.7Medical Application

6.2.8End of Topic Test - Synapses

6.2.9A-A* (AO3/4) - Nervous Comm&Coord

6.3Muscle Contraction

6.3.1Skeletal Muscle

6.3.2Sliding Filament Theory

6.3.3Contraction

6.3.4Slow & Fast Twitch Fibres

6.3.5End of Topic Test - Muscles

6.3.6A-A* (AO3/4) - Muscle Contraction

6.4Homeostasis

6.4.1Overview of Homeostasis

6.4.2Blood Glucose Concentration

6.4.3Controlling Blood Glucose Concentration

6.4.4End of Topic Test - Blood Glucose

6.4.5Primary & Secondary Messengers

6.4.6Diabetes Mellitus

6.4.7Measuring Glucose Concentration

6.4.8Osmoregulation

6.4.9Controlling Blood Water Potential

6.4.10ADH

6.4.11End of Topic Test - Diabetes & Osmoregulation

6.4.12A-A* (AO3/4) - Homeostasis

7Genetics & Ecosystems (A2 only)

7.1Genetics

7.1.1Key Terms in Genetics

7.1.2Inheritance

7.1.3Linkage

7.1.4Multiple Alleles & Epistasis

7.1.5Chi-Squared Test

7.1.6End of Topic Test - Genetics

7.1.7A-A* (AO3/4) - Genetics

7.2Populations

7.2.1Populations

7.2.2Hardy-Weinberg Principle

7.3Evolution

7.3.1Variation

7.3.2Natural Selection & Evolution

7.3.3End of Topic Test - Populations & Evolution

7.3.4Types of Selection

7.3.5Types of Selection Summary

7.3.6Overview of Speciation

7.3.7Causes of Speciation

7.3.8Diversity

7.3.9End of Topic Test - Selection & Speciation

7.3.10A-A* (AO3/4) - Populations & Evolution

7.4Populations in Ecosystems

7.4.1Overview of Ecosystems

7.4.2Niche

7.4.3Population Size

7.4.4Investigating Population Size

7.4.5End of Topic Test - Ecosystems & Population Size

7.4.6Succession

7.4.7Conservation

7.4.8End of Topic Test - Succession & Conservation

7.4.9A-A* (AO3/4) - Ecosystems

8The Control of Gene Expression (A2 only)

8.1Mutation

8.1.1Mutations

8.1.2Effects of Mutations

8.1.3Causes of Mutations

8.2Gene Expression

8.2.1Stem Cells

8.2.2Stem Cells in Disease

8.2.3End of Topic Test - Mutation & Gene Epression

8.2.4A-A* (AO3/4) - Mutation & Stem Cells

8.2.5Regulating Transcription

8.2.6Epigenetics

8.2.7Epigenetics & Disease

8.2.8Regulating Translation

8.2.9Experimental Data

8.2.10End of Topic Test - Transcription & Translation

8.2.11Tumours

8.2.12Correlations & Causes

8.2.13Prevention & Treatment

8.2.14End of Topic Test - Cancer

8.2.15A-A* (AO3/4) - Gene Expression & Cancer

8.3Genome Projects

8.3.1Using Genome Projects

8.4Gene Technology

8.4.1Recombinant DNA

8.4.2Producing Fragments

8.4.3Amplification

8.4.4End of Topic Test - Genome Project & Amplification

8.4.5Using Recombinant DNA

8.4.6Medical Diagnosis

8.4.7Genetic Fingerprinting

8.4.8End of Topic Test - Gene Technologies

8.4.9A-A* (AO3/4) - Gene Technology

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Mutations

Causes of Mutations