11.1. Mutations

Genetic mutations

The DNA as hereditary material transmitted with great fidelity to the next generations. Although DNA polymerases synthesize DNA with a very low error rate and have mechanisms to repair their errors, alterations do occasionally occur. These changes produced in DNA replication are mutations.

Hugo de Vries, in addition to being one of those who rediscovered Mendel's laws in 1900, was the first to use the term mutation when studying the sudden changes that appeared in the offspring of some Oenothera lamarkiana plants. He defined mutation as "any heritable change in hereditary material that cannot be explained by segregation or recombination."

This definition changed when it became known that the hereditary material is DNA and the double helix structure of DNA (Watson and Crick, 1953). Mutation was defined as any change in the nucleotide sequence of DNA.

The DNA changes also involve changes in the sequence of amino acids constituting the protein corresponding, so that mutations can affect survival of the organism.

Mutations can be classified according to several criteria:

According to the type of cells that are affected:
- Somatic: They are not inherited, since they are only transmitted to cells that originate from mitosis. They are the majority.
- Germ: They affect the gametes or the cells that produce them, and are transmitted to the offspring.
According to the cause that originated them:
- Natural or spontaneous.
- Induced by mutagens. The causes of these mutations will be discussed in another section.
According to the effects it produces in the body:
- Beneficial. Some mutations (less than 1%) improve the function of the protein they encode.
- Harmful or deleterious.
- Neutral. They are silent, they neither benefit nor harm.

Jonsta247 [GFDL or CC BY-SA 4.0-3.0-2.5-2.0-1.0], via Wikimedia Commons

According to the type of alteration produced:
- Gene or point mutation: If it affects the nucleotide sequence of a single gene. For example, a change in a nucleotide pair.
- Chromosomal mutation: If it affects the gene sequence of a chromosome.
- Genomic mutation: If it generates a change in the number of chromosomes.

Although the mutation is passed on to the offspring, sometimes it may not manifest itself. If it is a dominant character, it can be easily appreciated, but if it is recessive, it is difficult to detect it, since it only manifests itself if the individual is homozygous recessive.

The mutation, along with the meiotic recombination, is the source of genetic variability that enables evolution.

Although there are only approximately 10^-5 mutations per gene and generation, in a diploid organism such as humans, with about 10⁵ genes, the mutations that each individual has at birth are 10^-5 * 10⁵ * 2 = 2 mutations, which is a considerable amount.

Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU)

Aragon. September 2018, option A, question 4. September 2014, option B, question 1.

Mutations (2.5 points)

a) Concept (0.5 points)

Aragon. June 2013, option B. Issue 4.

Reasonedly answer the following questions: (1 point)

a) After a hypothetical nuclear accident, the inhabitants of a nearby town were examined. It was observed that his genotype had suffered some alterations. Will their descendants inherit these alterations? Give reasons for your answer.

b) In this second hypothetical case, a spectacular fire broke out in a chemical industry that affected thousands of people causing severe skin burns. However, the descendants of these affected people were born without any disorder. Explain the reason.

Aragon. June 2012, option B, question 4 .

a) Could a population of genotypically identical organisms that reproduce asexually evolve if no mutations occurred? Reason for the answer. (0.5 points)

b) A fire has produced large changes in the phenotype, although not in the genotype, of individuals in a population of mice. Will those changes be inherited by descendants? (0.2 points) A chemical agent has produced changes in the genotype, although not in the phenotype, of the individuals in a population. Will those changes be inherited by descendants? (0.3 points). Reason for the answers.

Aragon. June 2009, option A. 4 . (2 points): June 2005, option B. Question 4 . - (2 points)

a) What are mutations?

b) Example of each one of the types that you know.

c) What biological significance do they have?

d) Is it possible that a single base change from a gene results in the same protein?

e) Is it possible that the change of a single base produces an identical protein, but much shorter?

f) Can a change in one base give rise to a totally different protein?

Navarra, July 2021, question 13

What is a mutation? What difference does it make if a mutation occurs in a somatic cell or if it occurs in a germ cell?

Fundamental ideas about mutations

The mutations are changes that occur in the random DNA.

If the mutation occurs in a somatic cell, the mutation will affect only the individual who has it, without being passed on to their descendants.
If the mutation occurs in a germ cell, whose function is to join another germ cell to generate a new generation of individuals, it will be transmitted to the descendants.

Licensed under the Creative Commons Attribution Share Alike License 4.0

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Skip navigation Biology 2nd Baccalaureate Biology 2nd Bac. 1. Bioelements and biomolecules. Water and mineral salts 1.1. Chemical bonds in biology 1.1.1. Intramolecular bonds 1.1.1.1. Covalent bond 1.1.1.2. Ionic bond 1.1.2. Intermolecular bonds 1.1.2.1. Van der Waals forces 1.1.2.2. Hydrogen bonds 1.2. The chemical basis of life: inorganic and organic components 1.2.1. Primary bioelements 1.2.2. Secondary bioelements 1.2.3. Trace elements 1.3. The immediate principles or biomolecules 1.3.1. Water 1.3.1.1. Chemical structure of water 1.3.1.2. Properties and functions of water 1.3.2. Mineral salts 1.3.2.1. Functions of salts in solution 1.3.2.2. Colloidal solutions and dispersions 1.3.2.3. Properties of colloidal dispersions 1.3.2.4. Diffusion, osmosis and dialysis 1.3.2.4.1. Diffusion 1.3.2.4.2. Osmosis 1.3.2.4.3. Dialysis 1.4. Bibliography 2. Glucides 2.1. Glucid concept 2.2. Classification of carbohydrates 2.3. Monosaccharides 2.3.1. Trioses 2.3.1.1. Spatial isomerism or stereoisomerism 2.3.2. Tetroses 2.3.3. Pentoses 2.3.3.1. Monosaccharide cyclization 2.3.4. Hexoses 2.4. The N-glucosidic and O-glucosidic bonds 2.4.1. Substances derived from monosaccharides 2.5. Disaccharides 2.6. Polysaccharides 2.6.1. Homopolysaccharides 2.6.1.1. Reserve homopolysaccharides 2.6.1.2. Structural homopolysaccharides 2.6.2. Heteropolysaccharides 2.6.3. Heterosides 2.7. General functions of glucides 2.8. Bibliography 3. Lipids 3.1. Lipid concept 3.2. Classification of lipids 3.2.1. Fatty acids 3.2.1.1. Saturated and unsaturated fatty acids 3.2.1.2. Chemical properties of fatty acids 3.2.1.3. Physical properties of fatty acids 3.2.1.4. Fatty Acid Functions 3.2.2. Saponifiable lipids or with fatty acids 3.2.2.1. Simple lipids 3.2.2.1.1. Acylglycerides 3.2.2.1.2. Cerides 3.2.2.2. Complex lipids 3.2.2.2.1. Phospholipids 3.2.2.2.2. Glycolipids 3.2.3. Unsaponifiable lipids or without fatty acids 3.3. Lipid functions 3.4. Bibliography 4. Proteins 4.1. Introduction to proteins 4.2. Amino acids 4.2.1. Classification of amino acids 4.2.2. Properties of amino acids 4.3. The peptide bond 4.4. Protein 4.4.1. Protein structure 4.4.1.1. Primary structure of proteins 4.4.1.2. Secondary structure of proteins 4.4.1.3. Tertiary structure of proteins 4.4.1.4. Quaternary structure of proteins 4.4.2. Protein properties 4.4.3. Classification of proteins 4.4.3.1. Holoproteins 4.4.3.2. Heteroproteins 4.4.4. Protein functions 4.5. Enzymes 4.5.1. Structure of enzymes 4.5.2. The active center of enzymes 4.5.3. General Mechanism of Enzyme Catalysis 4.5.4. Regulation of enzyme activity 4.5.5. Allosteric enzymes 4.5.6. Nomenclature and classification of enzymes 4.6. The vitamins 4.6.1. Fat-soluble vitamins 4.6.2. Water soluble vitamins 4.7. Bibliography 5. Nucleotides and nucleic acids 5.1. The chemical composition of nucleic acids 5.1.1. Components of nucleic acids 5.1.2. Concept, types and functions of nucleic acids 5.1.3. Nucleosides 5.1.4. Nucleotides 5.1.4.1. Nucleotide functions 5.1.5. Nucleic acids 5.2. Deoxyribonucleic acid (DNA) 5.2.1. DNA structure 5.2.1.1. Primary structure of DNA 5.2.1.2. Secondary structure of DNA 5.2.1.3. Tertiary structure of DNA 5.2.1.3.1. Tertiary structure of DNA in prokaryotes 5.2.1.3.2. Tertiary structure of DNA in eukaryotes 5.2.1.4. Quaternary structure of DNA 5.2.2. DNA types 5.2.3. Genetic material: chromatin and chromosomes 5.2.3.1. Karyotype and karyogram 5.3. Ribonucleic acid (RNA) 5.3.1. RNA types 5.3.1.1. Transfer RNA 5.3.1.2. Messenger RNA 5.3.1.3. Ribosomal RNA 5.3.1.4. Nucleolar RNA 5.3.1.5. Small nuclear RNA 5.3.2. Functions of ribonucleic acids 5.4. Bibliography 6. Cell morphology 6.1. Cell concept 6.1.1. Cell history 6.1.2. Cell theory 6.2. Levels of cellular organization 6.2.1. General characteristics of cells 6.2.2. Prokaryotic cells 6.2.2.1. Prokaryotic cell morphology 6.2.2.2. Structure of prokaryotes 6.2.2.2.1. Bacterial capsule 6.2.2.2.2. Bacterial wall 6.2.2.2.3. Plasma membrane 6.2.2.2.4. Cytoplasm-Ribosomes-Inclusions 6.2.2.2.5. Bacterial DNA 6.2.2.2.6. Bacterial appendages 6.2.2.3. Bacteria Physiology 6.2.3. Eukaryotic cells 6.2.3.1. Animal and plant cell 6.2.3.1.1. Animal eukaryotic cell 6.2.3.1.2. Plant eukaryotic cell 6.2.3.2. Cell Evolution: Endosymbiont Theory 6.3. Size, shape and quantity 6.4. The plasma membrane 6.4.1. Chemical composition of the membrane 6.4.2. The structure of the membrane. The fluid mosaic model 6.4.3. Functions of the plasma membrane 6.4.4. Transport across the membrane 6.4.4.1. Small molecule transport 6.4.4.2. Macromolecule transport 6.4.5. Plasma membrane differentiations 6.5. The cell wall of plant cells 6.5.1. Chemical composition of the cell wall 6.5.2. Cell wall structure 6.5.3. Cell wall differentiations 6.5.4. Cell wall functions 6.6. Extracellular matrix or glucocalyx 6.7. Cytosol or hyaloplasm 6.8. The cytoskeleton 6.8.1. Microfilaments or actin filaments 6.8.2. Intermediate filaments 6.8.3. Microtubules 6.9. Cell membrane and organelle systems 6.9.1. Membrane systems 6.9.1.1. The endoplasmic reticulum 6.9.1.2. Golgi apparatus 6.9.2. Cell organelles 6.9.2.1. Lysosomes 6.9.2.2. Peroxisomes 6.9.2.3. Vacuoles 6.9.2.4. Mitochondria 6.9.2.4.1. Functions of the mitochondria 6.9.2.5. Plastids 6.9.2.5.1. Chloroplasts 6.9.2.6. Ribosomes 6.9.2.7. Centrosome 6.9.2.8. Cilia and flagella 6.10. Cell motility 6.11. The cell nucleus 6.11.1. Characteristics of the cell nucleus 6.11.2. The interphase nucleus 6.11.3. The mitotic nucleus or nucleus in division 6.12. Bibliography 7. Metabolism 7.1. Metabolism 7.1.1. Energetic Aspects of Cellular Chemical Reactions 7.2. Catabolism 7.2.1. Catabolism and obtaining energy 7.2.2. Carbohydrate catabolism 7.2.2.1. Glycolysis 7.2.2.2. Cellular respiration 7.2.2.2.1. Oxidative decarboxylation 7.2.2.2.2. Krebs cycle 7.2.2.2.3. Electron transport chain 7.2.2.2.4. Energy balance of cellular respiration 7.2.2.3. Fermentations 7.2.2.3.1. Alcoholic or ethyl fermentation 7.2.2.3.2. Lactic fermentation 7.2.2.3.3. Other types of fermentations 7.3. Anabolism 7.3.1. Autotrophic anabolism 7.3.2. Photosynthesis 7.3.2.1. Photochemical or light phase 7.3.2.1.1. Photosystems 7.3.2.1.2. Photophosphorylation 7.3.2.1.2.1. Non cyclic photophosphorylation 7.3.2.1.2.2. Cyclic photophosphorylation 7.3.2.2. Biosynthetic or dark phase 7.3.2.3. Factors influencing photosynthesis 7.3.2.4. Products of photosynthesis 7.3.3. Chemosynthesis 7.4. Bibliography 8. Cell reproduction 8.1. The cell cycle 8.1.1. Interphase 8.1.2. Cellular division 8.2. Cellular division 8.2.1. Mitosis 8.2.1.1. Prophase 8.2.1.2. Metaphase 8.2.1.3. Anaphase 8.2.1.4. Telophase 8.2.1.5. Cytokinesis 8.2.1.6. More on mitosis 8.2.2. Meiosis 8.2.2.1. Meiosis I 8.2.2.2. Meiosis II 8.2.3. Meiosis and sexual reproduction 8.2.4. Meiosis and life cycle 8.2.5. Biological importance of meiosis 8.3. Differences and similarities between mitosis and meiosis 8.4. Bibliography 9. Classical genetics 9.1. Genetics basics 9.2. Mendelian genetics 9.2.1. The method 9.2.2. Mendel's Laws 9.2.2.1. Mendel's first law or principle of uniformity in the first generation 9.2.2.2. Mendel's second law or principle of segregation 9.2.2.2.1. Backcross and test crossover 9.2.2.3. Mendel's third law or principle of independent combination 9.3. Gene interaction 9.3.1. Gene interaction between allelic genes 9.3.2. Gene interaction between non-allelic genes that influence for the same trait 9.4. Chromosomal theory of heredity 9.5. Ligation and recombination 9.6. Complex mendelism 9.6.1. Multiple allelism 9.6.1.1. Lethal genes 9.6.2. Pleiotropy 9.6.3. Expressiveness and genetic penetrance 9.7. Sex-linked inheritance 9.7.1. Y-linked inheritance 9.7.2. X-linked inheritance 9.8. Heredity influenced by sex 9.9. Bibliography 10. Molecular genetics 10.1. DNA as hereditary material 10.2. DNA replication 10.2.1. The need for DNA replication 10.2.2. First hypotheses about DNA duplication 10.2.3. Meselson and Stahl experiment 10.2.4. The sense of growth of the new strands 10.2.5. Mechanism of DNA replication 10.2.5.1. Replication in prokaryotes 10.2.5.2. Replication in eukaryotes 10.2.6. Error correction 10.2.7. Enzymes involved in replication 10.3. Gene concept 10.4. "One gene-one enzyme" theory 10.5. Transcription 10.5.1. Mechanism of transcription 10.5.1.1. Transcription in prokaryotes 10.5.1.2. Eukaryotic transcription 10.6. Translation or protein biosynthesis 10.6.1. The genetic code 10.6.2. Mechanism of translation of RNA to proteins 10.6.2.1. Translation in eukaryotes 10.7. Regulation of gene expression 10.8. Bibliography 11. Genetics and evolution 11.1. Mutations 11.2. Types of mutations 11.2.1. Gene or point mutation 11.2.2. Chromosomal or structural mutation 11.2.3. Mutation at the genomic level 11.3. Causes of mutations 11.4. Evolutionary implications of mutations 11.5. Metabolic implications of mutations 11.6. Bibliography 12. Microbiology and biotechnology 12.1. Microbiology 12.2. Viruses 12.2.1. Viral morphology 12.2.2. Viral physiology 12.2.2.1. Lytic cycle 12.2.2.2. Lysogenic cycle 12.2.2.3. Cycles of viruses of special interest 12.2.2.3.1. Flu virus life cycle 12.2.2.3.2. Life cycle of the AIDS virus 12.3. Other acellular forms 12.3.1. Viroids 12.3.2. Prions 12.4. Biotechnology 12.5. Bibliography 13. Immunology 13.1. Infection concept 13.2. Defense mechanisms against infections 13.2.1. Nonspecific mechanisms 13.2.1.1. Primary barriers: external defenses 13.2.1.2. Secondary barriers: internal defenses 13.2.2. Specific mechanisms 13.3. Immunity and immune system 13.3.1. Components of the immune system 13.3.2. Concept and nature of antigens 13.4. The immune response 13.4.1. Humoral immune response: the antibodies 13.4.1.1. Antibody-producing cells: B lymphocytes 13.4.1.2. Antibodies 13.4.1.2.1. Types of antibodies 13.4.1.2.2. Antigen-antibody reaction 13.4.1.3. Immune memory: primary and secondary responses 13.4.2. Cellular immune response: T lymphocytes 13.5. Types of immunity 13.5.1. Natural immunity 13.5.2. Artificial immunity 13.6. Immune system disorders 13.6.1. Autoimmunity 13.6.2. Hypersensitivity 13.6.3. Immunodeficiency 13.6.4. Transplants and the phenomenon of rejections 13.7. Bibliography « Previous \| Next » 11.1. Mutations Genetic mutations The DNA as hereditary material transmitted with great fidelity to the next generations. Although DNA polymerases synthesize DNA with a very low error rate and have mechanisms to repair their errors, alterations do occasionally occur. These changes produced in DNA replication are mutations. Hugo de Vries, in addition to being one of those who rediscovered Mendel's laws in 1900, was the first to use the term mutation when studying the sudden changes that appeared in the offspring of some Oenothera lamarkiana plants. He defined mutation as "any heritable change in hereditary material that cannot be explained by segregation or recombination." This definition changed when it became known that the hereditary material is DNA and the double helix structure of DNA (Watson and Crick, 1953). Mutation was defined as any change in the nucleotide sequence of DNA. The DNA changes also involve changes in the sequence of amino acids constituting the protein corresponding, so that mutations can affect survival of the organism. Mutations can be classified according to several criteria: According to the type of cells that are affected: Somatic: They are not inherited, since they are only transmitted to cells that originate from mitosis. They are the majority. Germ: They affect the gametes or the cells that produce them, and are transmitted to the offspring. According to the cause that originated them: Natural or spontaneous. Induced by mutagens. The causes of these mutations will be discussed in another section. According to the effects it produces in the body: Beneficial. Some mutations (less than 1%) improve the function of the protein they encode. Harmful or deleterious. Neutral. They are silent, they neither benefit nor harm. Jonsta247 [GFDL or CC BY-SA 4.0-3.0-2.5-2.0-1.0], via Wikimedia Commons According to the type of alteration produced: Gene or point mutation: If it affects the nucleotide sequence of a single gene. For example, a change in a nucleotide pair. Chromosomal mutation: If it affects the gene sequence of a chromosome. Genomic mutation: If it generates a change in the number of chromosomes. Although the mutation is passed on to the offspring, sometimes it may not manifest itself. If it is a dominant character, it can be easily appreciated, but if it is recessive, it is difficult to detect it, since it only manifests itself if the individual is homozygous recessive. The mutation, along with the meiotic recombination, is the source of genetic variability that enables evolution. Although there are only approximately 10^-5 mutations per gene and generation, in a diploid organism such as humans, with about 10⁵ genes, the mutations that each individual has at birth are 10^-5 * 10⁵ * 2 = 2 mutations, which is a considerable amount. Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU) Aragon. September 2018, option A, question 4. September 2014, option B, question 1. Mutations (2.5 points) a) Concept (0.5 points) Aragon. June 2013, option B. Issue 4. Reasonedly answer the following questions: (1 point) a) After a hypothetical nuclear accident, the inhabitants of a nearby town were examined. It was observed that his genotype had suffered some alterations. Will their descendants inherit these alterations? Give reasons for your answer. b) In this second hypothetical case, a spectacular fire broke out in a chemical industry that affected thousands of people causing severe skin burns. However, the descendants of these affected people were born without any disorder. Explain the reason. Aragon. June 2012, option B, question 4 . a) Could a population of genotypically identical organisms that reproduce asexually evolve if no mutations occurred? Reason for the answer. (0.5 points) b) A fire has produced large changes in the phenotype, although not in the genotype, of individuals in a population of mice. Will those changes be inherited by descendants? (0.2 points) A chemical agent has produced changes in the genotype, although not in the phenotype, of the individuals in a population. Will those changes be inherited by descendants? (0.3 points). Reason for the answers. Aragon. June 2009, option A. 4 . (2 points): June 2005, option B. Question 4 . - (2 points) a) What are mutations? b) Example of each one of the types that you know. c) What biological significance do they have? d) Is it possible that a single base change from a gene results in the same protein? e) Is it possible that the change of a single base produces an identical protein, but much shorter? f) Can a change in one base give rise to a totally different protein? Navarra, July 2021, question 13 What is a mutation? What difference does it make if a mutation occurs in a somatic cell or if it occurs in a germ cell? Fundamental ideas about mutations The mutations are changes that occur in the random DNA. If the mutation occurs in a somatic cell, the mutation will affect only the individual who has it, without being passed on to their descendants. If the mutation occurs in a germ cell, whose function is to join another germ cell to generate a new generation of individuals, it will be transmitted to the descendants. Licensed under the Creative Commons Attribution Share Alike License 4.0 « Previous \| Next » These pages are semi-automatically translated from the web Biology 2nd Baccalaureate. Biología de 2º de Bachillerato (biologia-geologia.com). You can make any suggestion, question, comment, ..., in our forum 2º Bachillerato Biología - Foro de biologia-geologia.com
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Genetic mutations