HSC Biology Module 6: Genetic Change

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Module 6: Genetic Change

Contents

Mutation

Mutation: random changing of a gene that results in genetic variation.

Explain how a range of mutagens operate, including but not limited to:

Electromagnetic radiation sources

Energy from radiation sources displaces an electron from its shell → creates an ion with charge → breaks chemical bonds → damages DNA.

Chemicals

Intercalating agents: chemicals that disturb bonds between bases → error in DNA replication.

Base analogues: chemicals that replace bases → DNA does not have correct base sequence and cannot function.

DNA reactive chemicals: chemicals that react with DNA → forms cross-links or breaks DNA strands.

Naturally occurring mutagens

Interfere with oncogenes and tumour-suppressor genes.

Viruses

Direct: carry oncogenes or enhance the cell’s proto-oncogenes → forms tumour → cancer.

Indirect: cause chronic inflammation → causes cancer.

Transposable element: short DNA sequences that,

– Cause errors in replication and chromosome duplication.

– Insert themselves into the middle of a gene → stops gene functioning.

Compare the causes, processes and effects of different types of mutation, including but not limited to: – point mutation – chromosomal mutation

Point Mutation: adds/removes 1 (or very few) nucleotides from DNA/RNA.

Point mutation

Substitution mutation

Frameshift mutation

Silent mutation

Missense mutation

Nonsense mutation

Nucleotide insertion

Nucleotide deletion

Causes/ processes

Substitution of a base occurs but same amino acid is coded for.

Substitution of a base occurs but different amino acid is coded for.

Substitution of a base occurs but a stop codon is produced = stops protein synthesis.

Adds 1 or 2 nucleotides and pushes all proceeding nucleotides out of order.

Removes 1 or 2 nucleotides and pulls all proceeding nucleotides out of order.

Effect

No observable effect (since same amino acid).

Incorrect polypeptide.

Shorter and incorrect polypeptide chain.

Incorrect polypeptide.

Incorrect polypeptide.

Chromosomal Mutation: mutations that changes many nucleotides.

Chromosomal mutation

Duplication

Inversion

Deletion

Insertion

Translocation

Causes/ processes

Replication of a section of nucleotides.

Section of nucleotides break off, reverse order and reattach.

Remove section of nucleotides.

Section of nucleotides break off and attach to a different chromosome.

A segment/ entire chromosome attaches/switches with another chromosome.

Effect

Pushes all nucleotide out of order = incorrect polypeptide.

Incorrect nucleotide order = incorrect polypeptide.

Shorter polypeptide chain.

Changes nucleotide sequence of chromosome = incorrect functioning.

Changes nucleotide sequence of chromosome = incorrect functioning.

Chromosomal Abnormalities: mutations that involves WHOLE chromosomes (or changes number of chromosomes).

Chromosomal abnormalities

Aneuploidy

Polyploidy

Causes/processes

Extra or missing chromosome usually from homologous chromosomes not separating in 1st meiotic division e.g. down syndrome.

Contains more than 2 corresponding chromosomes. Results from gametes being diploid (not haploid).

Images



Distinguish between somatic mutations and germ-line mutations and their effect on an organism

Somatic mutation Germ-line mutation
Definition Occur in body cells during mitosis and only affects the individual. Occur in germ cells which become gametes and affects offspring of the individual.
Effect – Error in DNA = more susceptible to developing cancer.- Mosaicism: mutated cell divides to produce more cells with mutated genome e.g. port-wine stain. – Mutate offspring.- Introduce new alleles into a population = natural selection.

Assess the significance of ‘coding’ and ‘non-coding’ DNA segments in the process of mutation

Coding DNA

Non-coding DNA

Codes for and produces amino acids and polypeptides. Does not code for amino acids and polypeptides but is essential for proper cell functioning.

Intron Mutations

  • Introns: Non-coding parts of DNA that are removed when mRNA is produced.
  • Mutation → introns are not removed when mRNA is produced → incorrect mRNA → incorrect coding for polypeptides.

Promoter and Terminator Mutations

  • Over or under production of gene product.

Non-Coding RNA Mutations

  • Mutation to non-coding RNA in mitochondrial genome → amino acid cannot be added to mitochondrial proteins → reduces effectiveness of cellular respiration → mitochondrial disease.

Thus, despite mutations occurring in non-coding parts of DNA they still have significant health consequences.

Investigate the causes of genetic variation relating to the processes of fertilisation, meiosis and mutation

The processes that cause genetic variation are,

Meiosis: crossing over, random segregation and independent assortment.

Fertilisation: random fusing of genetically recombined gametes during fertilisation increases genetic variation.

Mutation: somatic or germ line mutation introduce new alleles.

Crossing over

Evaluate the effect of mutation, gene flow and genetic drift on the gene pool of populations

Gene pool: all the genes in a population.

Genetic drift: random change in allele frequency by chance (unlike natural selection which is not based on chance but on which alleles are most favourable).

Gene flow: passing on genetic material from one population to another e.g. pollen blown to a new area.

Mutation Gene flow Genetic drift
Effect on gene pool of population Introduces new alleles which enter the gene pool = increases gene pool. Recombines DNA between population = increases gene pool. As a particular allele increases in frequency, it decreases the frequency of other alleles = decreases gene pool.

Biotechnology

Investigate the uses and applications of biotechnology (past, present and future), including:

Analysing the social implications and ethical uses of biotechnology, including plant and animal examples

Selective Breeding

Plant example

Animal example

5000BC corn had small cobs and few kernels. 1500AD corn was large with lots of kernels due to selective breeding. Selective breeding: Mule was bred from the female horse and male donkey. Mules helped transport because of their strength and endurance.

Fermentation: Microorganisms breakdown sugar in an anaerobic environment. This process was used to make bread, wine and cheese.

Vinegar: Acidity prevents food spoilage.

Pasteurisation (developed after Mendel and Pasteur’s discoveries of biological processes): Remove pathogens from food.

DNA profiling/sequencing (modern biotechnologies): Study/decrease genetic/infectious diseases and providing early detection of diseases.

Social Implications

Benefits Disadvantages
Greater access to goods/services.E.g. Recombinant DNA technology removes and inserts genes from viruses into humans as a vaccination. Patenting: Companies control/own biotechnologies → companies can control prices of biotechnologies and make them unaffordable → social inequality.
Improve nutrition/yield of crops → reduces mass starvation and poverty.E.g. Golden rice (transgenic species) was genetically modified to contain vitamin A. Vitamin A is essential for eyesight and a healthy immune system. Privacy: Biotechnologies reveal personal information which can be misused. E.g. an insurance company does not grant life insurance for an individual predisposed to a disease detected through genetic screening.
Unknown health effects.E.g. Genetically modified foods may be toxic or change the consumer’s DNA.

Ethical Thoughts

  • Philosophy, culture and religion – biotechnology interrupts the natural balance.
  • Genetic abnormalities in embryos can be identified leaving parents with the choice to terminate pregnancy. Ending life during pregnancy is controversial.
  • Legislations regarding biotechnologies have ‘grey areas’ e.g. who legally has access to private information (employers, insurers etc.).
  • Biotechnology has unknown health effects = bad animal welfare e.g. transgenic pigs grow very quickly which negatively impacts their joints.

Researching future directions of the use of biotechnology

Medicine: Improved treatment and detection of diseases.

E.g. gene therapy involves inserting healthy genes to replace defective genes.

E.g. stem cell research involves using unspecialised cells to replace diseased tissue with healthy tissue.

Agriculture: Sustainable food production methods to meet increasing population (increasing demand).

Evaluating the potential benefits for society of research using genetic technologies

Improved medicine

  • Improved/early diagnosis of diseases and predisposition to diseases = early intervention and prevention = better community health.
  • New vaccines.
  • E.g. Current research: turn off gene in muscles to stop muscular dystrophy.
  • E.g. Current research: nanoparticles which contain anti-cancer drugs are being delivered to cancer cells (without damaging healthy surrounding cells).

 

Higher quality/quantity food = improves nutrition

  • Genetically modified crops have favourable traits that make them disease/pest tolerant, more efficient and better quality.
  • E.g. GM crops have genes that increase vitamin levels → helps malnutrition.

 

Evaluating the changes to the Earth’s biodiversity due to genetic techniques

Genetic techniques have both decreased and conserved biodiversity in different ways.

Decrease in biodiversity

  • GM crops involves selecting favourable traits and breeding them →fewer crop varieties → decreases gene pool. If environmental change occurs an entire species could be wiped out because there is limited variation → less food for growing population.
  • GM crops have had unexpected effects on native plants or soil microbes → decreases native population → loss of biodiversity.
  • GM animals may interbreed with native populations that have the same gene (transgene) as the GM animal → transgene becomes more abundant and other genes die out → decreases gene pool.

Conservation of biodiversity

  • GM crops → increased crop productivity without destroying large amount of land → reduces land clearing → preserves habitats → conserves biodiversity.
  • GM crops can reintroduce genes that have died out → increases gene pool.
  • Genetic techniques can predict the genes of offspring → helps select individuals for breeding programs → helps endangered species. E.g. Northern quolls are endangered and genetic techniques help select which individuals to breed.
  • Artificial insemination and pollination introduce genes into a population → increases gene pool → increases biodiversity.

Genetic technologies

Investigate the uses and advantages of current genetic technologies that induce genetic change

REPRODUCTIVE TECHNOLOGIES

Artificial insemination: Artificially introduced sperm into female.

  • E.g. Cattle with more beef or higher milk production.
Advantages Disadvantages
Frozen sperm stored indefinitely and transported anywhere. Overuse of same sperm = decreases genetic diversity and recessive characteristics = genetic diseases.
Desirable characteristics from specific male can be passed onto generations.
Farmers do not have to maintain cost and health of a male animal health since they just need sperm.
Females inseminated after death of male.
Animal conservation of endangered species e.g. gorillas.
In humans it is helpful when male/female cannot engage in sexual intercourse.
Overcomes geographical barriers, allowing genes to be spread worldwide.

NOTE IVF is not artificial insemination since the egg is fertilised outside the body.

Artificial pollination: Remove pollen and brush on stigma of plant.

Advantages Disadvantages
Higher yield, larger fruit and disease resistance. Overuse of 1 strain = susceptible to pest/disease.
Conserves plant biodiversity.
Saves endangered species.

Compare the processes and outcomes of reproductive technologies, including but not limited to: – artificial insemination – artificial pollination

Artificial insemination

Artificial pollination

Used in animals.

Used in plants.

Injection of sperm into an egg using a pipette.

Dusting of pollen onto stigma often by hand.

Similarities

– Recombine genes.

– Increase favourable gene frequency in a population.

– Female and male gametes combine.

Investigate and assess the effectiveness of cloning, including but not limited to: – whole organism cloning – gene cloning

Clone: Genetically identical copy of another organism.

WHOLE ORGANISM CLONING

Artificial embryo twinning

Somatic cell nuclear transfer

Early embryo is split in two → embryos put in a surrogate mother.

Remove single set of chromosomes from egg cell → insert nucleus of body cell from organism being cloned (body cells contain 2 sets of chromosomes) → egg cell divides → embryo placed into surrogate mother.

GENE CLONING

In vivo method

In vitro method

Incorporates specific gene into another organism.

Uses restriction enzymes, ligases and vectors.

Polymerase chain reaction produces many copies of a gene.

THERAPEUTIC CLONING

Cloning embryonic stem cells (unspecialised cells but can differentiate into specialised cells) for the treatment of disease.

Describe techniques and applications used in recombinant DNA technology, for example: – the development of transgenic organisms in agricultural and medical applications

Transgenic species: genes from species introduced into another species’ genome.

In step 5 the plasmids enter the bacteria in 1 of 2 ways:

i) Heat shock: Bacterial cells + recombinant plasmids + non-recombinant plasmids placed in cold solution → rapidly increase temperature → bacteria cell membrane is disrupted → plasmids enter bacteria.

ii) Electroporation: Bacterial cells + recombinant plasmids + non-recombinant plasmids are subjected to electricity → bacteria cell membrane is disrupted → plasmids enter bacteria.

Agricultural Application

Bt cotton (Bacillus thuringiensis): Naturally produces chemicals that kill insects. There is no longer a need for pesticides. The gene is isolated from the bacteria which produces a toxic protein harmless to humans and most animals.

Medical Application

Bacterial insulin: Gene for insulin from the human pancreas was inserted into pig. The pig rapidly produces insulin hormone cheaply. Needed for diabetic patients.

Evaluate the benefits of using genetic technologies in agricultural, medical and industrial applications

Agriculture

  • Artificial insemination

– Breeding animals for higher quality food + improves efficiency of food production. However there has been a decrease in fertility of cattle and horses since the introduction of this technology.

  • Cloning

– Beef and dairy cattle have been cloned to increase food production in agriculture e.g. in China pigs are being cloned to feed the large population. However these food products have not yet been deemed safe in Australia.

Medical

  • Artificial insemination

– Overcomes fertility problems allowing humans to conceive a child.

  • Cloning

– Xenotransplantation involves transplanting cells between humans to treat diseases e.g. replacing damaged brain cells with healthy ones to treat Parkinson’s and Alzheimer’s disease.

– Conservation of nearly extinct species e.g. Eggs of northern white rhinoceros have been collected and preserved from endangered females → future stem cell technology and IVF will increase population.

– Gene cloning = whole genome sequencing: map genes within the genome.

– Gene cloning = determine effect of environment on gene expression, examine mutations that lead to disease and understand the function of a gene e.g. it was found that a mutation to BRCA1 gene has a negative effect on the PTEN gene which causes uncontrolled cell division and leads to a tumour = breast cancer.

– Gene cloning = gene therapy: inserting gene into another organism’s cells to replace damaged genes that cause disease.

Industrial

  • Recombinant DNA technology makes synthetic enzymes e.g. amylase and lipase → develop pharmaceuticals, textile fabrics and detergent additives.

Evaluate the effect on biodiversity of using biotechnology in agriculture

Look in 8.1 for effects of biotechnology on biodiversity.

Example

  • Artificial insemination

Breeding Fresian dairy cows → higher milk production. But the native Ankole cattle are becoming threatened due to new competition (Ankole cattle are well-adapted to semi-arid conditions in Africa) → reduces biodiversity.

Interpret a range of secondary sources to assess the influence of social, economic and cultural contexts on a range of biotechnologies

Social: Areas where science is widely accepted enables the use of biotechnologies.

Economic: Wealthier countries/areas can afford to purchase and sustain biotechnologies.

Cultural: Positive reactions to change from people in an area where religion is not a governing force enables and encourages use of biotechnologies since science does not clash with cultural values.

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