Mutation: Types, Role, and Impact

Mutation Basics

• Is a change in the genetic material of a cell
• Occurs when the sequence of nucleotides (bases) in DNA is altered
• Can affect an organism's function if it occurs in proteins

Types of Mutations

• Spontaneous mutations are due to errors in DNA replication, transcription, cell division, or DNA repair mechanisms
• Induced mutations are caused by mutagens (environmental agents that alter DNA)
• Germline mutations occur in eggs and sperm and can be passed to offspring
• Somatic mutations occur in body cells and are not passed on

Role and Impact of Mutations

• Introduces new alleles and variation into a population
• Can be harmless, harmful, or provide a selective advantage

Electromagnetic Radiation as Mutagen

• Includes radio waves, microwaves, infrared, visible light, UV, X-rays, and Gamma rays
• Ionizing radiation can remove electrons from atoms, which breaks chemical bonds in DNA, causing mutations or cell death

Chemical Mutagens

• Cause mutations if cells are exposed at high frequencies or for prolonged periods
• Can be artificial or naturally occurring

Examples of Chemical Mutagens

• Ingested: alcohol, tar in tobacco smoke, some medications, charred food, and food additives & preservatives
• Environmental: asbestos, cleaning products, organic solvents, pesticides, and heavy metals

How Chemical Mutagens Work

• Intercalating agents insert into DNA bonds and alter its shape, leading to errors in replication
• Base analogs are similar to nitrogenous bases and can be incorporated into DNA, resulting in non-functional DNA
• DNA reactive chemicals react directly with DNA and cause breakages and crosslinks

What are Naturally Occurring Mutagens

• Some mutations are caused by mutagens already in the environment, increase in exposure or amount can cause mutations

Examples of Natural Mutagens

• Plants eg. cycad plant
• Animals eg. nitrates in deli meat
• Microbes (bacteria, viruses) e.g. HPV
• Can lead to cancer-causing gene overexpression or disrupt tumor-suppressor genes

Point Mutations

• Changes in base sequences of a single gene, potentially forming a new allele

Base Nucleotide Pair Substitution

• Silent mutations do not change the amino acid and protein (frequent)
• Missense mutations change the amino acid, altering the protein's meaning
• Nonsense mutations change the amino acid coding for a stop codon
• Alters protein shape/synthesis site, diminishing function

Base Nucleotide Pair Insertion/Deletion

• Can cause frameshift which leads to a translated polypeptide sequence change
• Unless insertion or deletion happens in multiples of 3 bases in a row

Single Nucleotide Polymorphism (SNP)

• Occurs when a point mutation is frequent within a population

Chromosomal Mutations

• Affect DNA at the chromosomal level, changing a section rather than a single nitrogenous base
• Affects more than one gene

Forms of Chromosomal Mutation

• Deletion: Loss
• Duplication: Repeating
• Inversion: Inverting
• Translocation: Rearranging

Aneuploidy

• Happens when whole chromosomes/sets are lost, gained, or rearranged
• Condition where a cell's chromosome number is more or less than normal

Non-Disjunction

• Occurs when homologous chromosome pairs fail to segregate during cell division

Chromosomal Deletion Effects

• Loss of a section of the chromosome
• Leads to the loss of multiple genes in the deleted section
• The cells will lack the proper genes for the mutation and will also lack behavioral traits

Chromosomal Insertion (Duplication) Effects

• A section of the chromosome copies itself and inserts
• Gametes will inherit an extra copy of genes
• Can lead to a imbalance in the gene dosage

Chromosomal Inversion Effects

• Section detaches itself and reattaches in flipped alignment
• Prevents crossing over during meiosis
• Reduces genetic variation in offspring

Chromosomal Translocation Effects

• Is when a section of one chromosome breaks off and joins a non-homologous chromosome
• Can cause the gamete to inherit something bad, either a reduced or duplicated gene set

Somatic Mutations

• Occur in body cells after conception, aren't passed onto offspring
• Mutations are carried in the daughter cells that are also mutant and impact specific tissues/cells
• Effects can vary on the part of the DNA, but are often local (e.g. cancers)

Germ-Line Mutations

• Germ line cells (gametes) carry DNA and transfer it after fertilization onto the next generation zygote
• Can be passed onto every cell after offspring, inherited diseases result
• Directly changes the allele frequency within a gene pool

Significance of Coding and Non-Coding Regions

• EXONS (coding regions) are transcribed and translated to make a protein.
• INTRONS (non-coding regions) are not expressed during gene expression and not translated into a protein and are taken out

Hox Genes

• Are found in animals and control the development of most organ systems
• Encode for proteins that target molecular switches on genes for the creation of new body parts

Intron Functions

• Regulates gene expression
• Mutations can result in no effect, prevention of polypeptide synthesis affecting protein functions, or birth defects
• Can cause predispositions to specific diseases, which messes with regulatory DNA sequences

Mutation and Gene Frequencies

• Mutation leads to new alleles, changing the phenotype and can often be a basis for good natural selection
• Is usually for detrimental, or deleterious mutations
• Can be neutral, beneficial, or for genetic drift

Factors of Genetic Variation

• Chance of surviving and reproducing, the changes of genetics due to random chance (genetic drift), and gene flow (movement of said genes in population)

Genetic Variation Factors Continued

• the founder effect, the loss of genetic variation
• The bottleneck effect: sharp reduction because of envents

Biotechnology

• Using living organisms or products in new ways to improve environments

Ancient Biotechnology (Pre 1800)

• Agriculture through domestication and selective breeding, and food production through yeast and cheese making

Classical Biotechnology (1800-1945)

• Fermentation, medicines, and selective breeding techniques

Modern Biotechnology (1945-present)

• Genetic Engineering, Gel electrophoresis, gene probes and DNA sequencing, and Reproductive technologies and genetic diversity

Benefits of Biotechnology

• Can give social benefits or have moral benefits
• Can give medical improvements, increase food production, reduce starvation, increase workforce production

Social Implications

• Include but not limited to; ethical and moral dilemmas, benefits outweighing detriments and costs of new product, social impact, threats to diversity, animal welfare

Biotechnology: Future Uses

• Influenced by new scientific discoveries, economics, the changing environment, ethical issues and needs for society
• Personalized medicine is made by using genetic data to tailor treatment to make the best treatments possible
• Genetic engineering will introduce and edit a single gene for a desirable trait

Biotechnology in Industry

• Biotechnology is used in: chemical processing, mining, metal refining, and alternate energy sources

Types of Biotechnology Examples

• Selective Breeding: Select male cattle to reproduce with a female
• IVF & Transgenic Organisms: Produce pest resistant corn

Assessing Changes to the Earth's Biodiversity Due to Genetic Techniques

• Advantages: better biodiversity in short term, new gene combinations in population, saves species, alleviate hunger, conserve biodiversity
• Disadvantages: reduction in biodiversity in the long term if good traits are reproduced, wild variety will crossbreed, reduce biodiversity overall

ATryn Goats

• Transgenic goat species chosen as bioreactors produce proteins in milk
• Used as transgenic animals with a human gene
• The extracted material prevents blood clotting

Defining Transgenesis

• Introducing a foreign gene (transgene) to give an organism traits
• Allow desirable traits that wouldn't happen naturally

Transgenesis

• Find gene, insert gene into bacteria or virus, develop cells until the bacteria multiplies, test

CRISPR

• Is a type of bacteria that can chop up attacking viruses
• Can snip at a base and attach an RNA base, uncovering genes linked to neurological disorders

Future Research Directions

• gene therapy
• GMOs
• plant banks
• resources to develop fuels.

Medicine & Healthcare Via Genetic Tech

• Gene Therapy: can treat genetic disorders by correcting faulty genes
• Personalized Medicine: helps specific medicine to be tailored to an individual
• Disease Prevention: Genetic screening allows for early disease detection

Agriculture & Food Production Via Genetic Tech

• Increased Crop Yield: make crop growth much easier
• Pest and Environment Resistence
• Nutritional Enhancement: GM foods can be enriched with vitamins, to combat malnutrition
• Reduced Pesticide Use: reduces the need of bad pesticides

Environmental Conservation Via Genetic Tech

• Gene help can fix, revive, and protect endangered species through creating more diversity
• Bioremediation has been shown to clean oil spills, plastic waste, and polluted areas

Comparing Outcomes of Reproductive Technologies

• Artificial stimulation involves collecting sperm and implanting it in the females
• Can often fix certain diseases through processes like invitro fertilization

Artificial Insemination (animals) Outcomes

• Transporting sperm overcomes the problem of transporting large animals over long distances
• Reduces danger to animals of injury during transport or mating
• Used in wildlife conservation to improve the reproductive success of endangered species

Disadvantages of Artificial Insemination (animals)

• Can be costly due to requirement of specialised equipment
• The female can be injured if the procedure is carried out incorrectly
• It can cause reduction in genetic diversity of populations around the world