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Genetic Engineering Notes

1) Key Definitions and Core Concepts

  • Genetic engineering (also called genetic modification):- The deliberate modification of characteristics of an organism by manipulating its genetic material with the use of biotechnology.

    • \text{Genetic engineering} = \text{ deliberate modification of genetic material using biotechnology}

  • Biotechnology:- The use of biological processes, organisms, or systems to manufacture products intended to improve the quality of human life.

    • Example: using bacteria to make cheese.

  • Genetically Modified Organism (GMO):- An organism produced through genetic engineering.

  • Bacteria as the first GMOs:- First GMOs created in 1973.

    • First GM mice generated in 1974.

    • Insulin-producing bacteria commercially produced in 1982.

    • Genetically modified food on the market since 1994.

  • Transgenic organism:- An organism that receives genetic material from another species.

  • Recombinant DNA technology:- Formation of new DNA from two different organisms in a recipient cell.

  • Cloning:- A type of genetic engineering aimed at duplicating the genes of an existing organism so the egg contains an identical set of genes.

    • Definition: the production of an individual genetically identical to the one from which it was produced.

  • Stem cells:- Actively dividing cells that can give rise to any of the other cells of the same organism.

    • They are unspecialized (undifferentiated) cells.

  • Cord blood:- Blood found in the umbilical cord; a rich source of stem cells.

2) Terminology and Quick References

  • Genetic engineering: \text{deliberate modification of characteristics via manipulating genetic material with biotechnology}

  • Biotechnology: \text{use of biological processes/organisms/systems to manufacture products for human benefit}

  • Genetically Modified Organism (GMO): \text{organism produced through genetic engineering}

  • Cloning: \text{production of an individual genetically identical to the original}

  • Stem cells: \text{actively dividing, undifferentiated cells that can become other cell types}

  • Cord blood: \text{blood from the umbilical cord, a stem cell source}

3) Genetically Modified Organisms (GMOs) and Recombinant DNA

  • Importance and applications of GMOs:- Synthesis of medicinal drugs

    • Production of new crops

    • Stem cell research

    • Cloning

  • Human insulin production via recombinant DNA technology:- Concept: Insulin gene is cloned and expressed in bacteria (e.g., E. coli) to produce insulin.

    • Key steps (summarized):

      1) DNA coding for insulin production is isolated from human pancreatic cells.

      2) Restriction enzymes cut the DNA into segments to isolate the insulin gene.

      3) E. coli bacteria are used to produce insulin.

      4) Plasmids (bacterial circular DNA) are used as carriers.

    • The process uses two main enzymatic actions:

    • Restriction enzymes cut DNA at specific sequences.

    • DNA ligase inserts DNA fragments, producing recombinant DNA.

    • Core concept equation:

    • \text{recombinant DNA} = \text{plasmid} + \text{human insulin gene}

    • Process outline (as described in slides):

    • Step 1: Cut the plasmid DNA and cut the human gene (restriction enzymes).

    • Step 2: Insert the human gene into the plasmid (DNA ligase) to form recombinant DNA.

    • Step 3: Introduce the recombinant plasmid into the host bacterium (e.g., E. coli).

    • Step 4: Engineered bacteria multiply and produce insulin.

    • Step 5: Recover, purify, and prepare human insulin for medical use.

    • Practical outcome: Insulin produced, purified, and used to treat diabetes.

  • Timeline snapshot:- 1973: First GMOs (bacteria).

    • 1974: First GM mice generated.

    • 1982: Insulin-producing bacteria commercialized.

    • 1994: Genetically modified food sold commercially.

4) Transgenic Organisms and Recombinant DNA Details

  • Transgenic organisms: organisms that receive genetic material from another species.

  • Recombinant DNA technology: creation of new DNA from two different organisms in a recipient cell.

  • Example applications: production of hormones (e.g., insulin), pest resistance in crops, production of pharmaceuticals.

5) Cloning

  • Cloning is a form of genetic engineering aimed at duplicating genes or creating genetically identical individuals.

  • Somatic Cell Nuclear Transfer (SCNT): an embryo is created by transferring a donor somatic cell nucleus into an enucleated egg cell.

  • Cloning examples: Dolly the sheep (first cloned mammal, 1996); Futi (cow cloned 2003 in South Africa).

  • Plant cloning: often achieved via cuttings (natural or artificial) to produce identical plants.

  • Advantages of cloning and genetic duplication include potential to produce fit (good genes) individuals, aid couples with fertility issues, disease resistance, and conservation of threatened species.

  • Ethical and practical concerns: unnatural, religious/cultural objections; reduced genetic variation; potential harms to cloned animals; high costs; long-term unknown effects.

6) Stem Cells and Cord Blood

  • Stem cells: actively dividing, undifferentiated cells capable of giving rise to various cell types.

  • Embryonic stem cells:- Derived from embryos; harvesting can be controversial due to destruction of embryos.

    • Current clinical use limited; potential to treat diseases like diabetes, leukemia, Alzheimer's, osteoporosis, sickle cell anemia.

  • Cord blood stem cells:- Collected from the cord blood post-birth; no embryo destruction.

    • Stored in cord blood banks; potential future therapies.

  • In vitro fertilization (IVF) context:- Eggs harvested, sperm provided, embryos formed; some embryos implanted, others frozen for future use.

    • Embryos from which stem cells may be harvested are sometimes the remaining frozen embryos; embryo destruction occurs if stem cells are harvested from embryonic sources.

  • Controversies and evolving approaches:- Harvesting embryonic stem cells raises ethical concerns about potential life.

    • Alternative sources (e.g., cord blood, 8-cell stage extraction) aim to avoid destroying embryos.

    • Advances show that removing one cell at the 8-cell stage can allow the embryo to continue developing, enabling stem cell harvest with reduced ethical concerns.

  • Cord blood banks:- South Africa has notable cord blood banks (e.g., in Cape Town).

    • Cord blood stem cells can be used for tissue/organ replacement in the future without immune rejection concerns.

7) In-Depth: CRISPR and Modern Genome Editing

  • CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats):- A revolutionary genome-editing system that enables highly targeted removal, addition, or alteration of DNA sequences with unprecedented precision.

    • Mechanism: CRISPR systems utilize a guide RNA (gRNA) molecule that is designed to match a specific DNA sequence. This gRNA then directs the Cas9 enzyme (or other CRISPR-associated nucleases) to the complementary DNA target.

    • Cas9 Enzyme: Once guided to the target, the Cas9 enzyme acts as molecular scissors, cutting the DNA double helix at the precise location specified by the gRNA.

    • Repair Mechanisms: After the DNA is cut, the cell's natural repair mechanisms are activated. Scientists can exploit these pathways to either inactivate a gene (non-homologous end joining, NHEJ) or insert a new piece of DNA (homology-directed repair, HDR) based on a provided template.

    • Applications: Beyond basic research, CRISPR applications include correcting genetic mutations responsible for diseases (e.g., cystic fibrosis, sickle cell disease), developing new gene therapies, creating disease-resistant crops, and producing livestock with desirable traits.

    • Ethical Considerations: The precision and ease of use of CRISPR raise significant ethical debates, particularly concerning germline editing (changes passed to future generations) and the potential for 'designer babies'. Regulation and societal consensus are crucial for its responsible application.

8) Genetic Modifications in Agriculture

  • Process overview:- Identify and isolate genes responsible for desirable traits.

    • Introduce these genes into plant cells that develop into adult plants carrying the traits.

  • Examples of desirable traits:- Pest resistance

    • Larger fruits/vegetables

    • Sweeter fruit/vegetables

    • Longer shelf life

  • Exam-style discussion points (as used in assessment):- Advantages include larger yields, stronger crops, disease resistance, and reduced environmental impact due to lower pesticide use.

    • Additional benefits cited: cheaper production for farmers, crops that survive under unfavourable conditions, improved crops for medical applications, and potential for reduced food waste.

  • Some cautions and ethical considerations:- Potential negative health effects (e.g., allergies, unknown long-term impacts of consuming GM foods), and biodiversity loss (e.g., if GM crops outcompete wild varieties or lead to monocultures).

    • High costs for seeds/biotech products; accessibility and equity concerns for small farmers in developing nations.

    • Intellectual property: seed company control and exclusive rights over regulated seeds, potentially limiting farmers' ability to save and replant seeds.

    • Ethical implications around modifying natural organisms, potential for unintended ecological consequences (e.g., superweeds, harm to non-target organisms), and questions of corporate control over global food supply.

9) Exam-Style Questions: Key Answers and Points

  • 3.1.1 What is meant by the term genome?- A genome is the organism’s complete set of genes.

  • 3.1.2 How does genetic engineering differ from selective breeding?- Genetic engineering involves transfer/manipulation of genes from one organism to another, whereas selective breeding relies on choosing parents with desirable phenotypes to produce offspring with desirable phenotypes.

  • 3.1.3 Why must products of genetic engineering undergo many tests?- To assess risks to human health and to determine if the transferred gene affects the expression of other genes and to test effectiveness of the product.

  • 3.1.4 Value of growing herbicide-resistant crops:- Herbicides can target weeds without harming crops, reducing competition and potentially increasing yield.

  • 3.1.5 Three additional advantages of genetic engineering in crop production (beyond those in the extract):- Produce crops resistant to adverse conditions (drought, pests).

    • Increase crop yields and shelf life of plant products.

    • Change ripening times to meet local and international demand; improve nutritional value and taste; introduce traits to meet population needs (e.g., vitamin A enhancement).

  • 3.1.6 Why seed companies insist on exclusive seed-selling rights?- Companies invest significant time and money into developing GM seeds; exclusive rights protect profits by controlling the seed market.

10) Historical Landmarks and Real-World Context

  • Milestones:- 1973: First GMOs (bacteria).

    • 1974: First GM mice.

    • 1982: Insulin-producing bacteria commercialized.

    • 1994: GM foods sold commercially.

    • 1996: Dolly the sheep, first cloned mammal, from an adult cell.

    • 2003: Futi, cloned cow in South Africa.

  • Real-world considerations:- GM crops and medicines provide significant benefits but require regulatory oversight, ethical debate, and ongoing monitoring for ecological and health impacts.

    • Cord blood banking presents non-embryo-destructive stem cell sources, contributing to the debate on the ethics of stem cell research.

11) Quick Reference: Common Relationships and Processes

  • Recombinant DNA workflow (summary):- Isolate gene of interest → cut gene with restriction enzymes → cut plasmid with same/compatible restriction enzymes → ligate gene into plasmid using DNA ligase → introduce recombinant plasmid into host organism (often bacteria) → host expresses gene → product purified for use (e.g., insulin).

    • Key enzymes: restriction enzymes (cut DNA) and DNA ligase (join DNA).

  • Core biological themes:- Manipulation of genetic material enables production of useful biomolecules, enhanced crop traits, and new disease models.

    • Ethical, environmental, and societal considerations influence adoption and regulation of biotechnologies.

12) Notes on Further Study and Integration

  • Review the differences between GMO, transgenic organisms, and cloning to avoid confusion.

  • Practice with the provided exam-style questions (3.1.1 to 3.1.6) and look for the 12-mark synthesis structure: short answers plus synthesis points.

  • Understand CRISPR at a conceptual level: targeted genome editing and ethical considerations related to its precision and potential off-target effects.

  • Be able to articulate both sides of stem