Lecture Notes on Cloning and Stem Cells

Cloning and Cell Differentiation Notes

Cloning and Its Implications

  • Cloned Embryos: Discussion on human clones, ethical concerns

  • Popular Culture References: Mentions from media (e.g., Dan's "Give Yourself the Gift of Yourself")

  • Fictional Illustration: Example about reanimating dead tissue, emphasizing a humorous tone

Cell Differentiation

  • Definition:

    • Cell differentiation is the process through which a generalized cell transforms into a specialized cell, such as neurons or red blood cells (RBCs).

  • Triggers:

    • Often chemically induced by neighboring cells leading to specialized functions.

  • Key Concepts:

    • Cell Fate: The specialized function a cell adopts.

    • Cell Potency: Refers to the potential range of different cell types that a stem cell can develop into, depending on the environment (includes the following types):

    • Totipotent Cells: Can develop into any cell type including extra-embryonic tissues.

    • Pluripotent Cells: Can give rise to nearly all cell types but not extra-embryonic tissues.

    • Cell Determination: Represents the stage when the potential of a stem cell is limited to a specific fate, with timing varying among cells.

    • Heterotopic Transplantation: A method employed to investigate cell potency and the timing of cell determination.

Developmental Biology

  • Stages of Development: Movement from fertilized egg to organogenesis.

    • Stages Illustrated:

    • (a) Fertilized eggs of frogs

    • (b) Newly hatched tadpoles

Cytoplasmic Determinants and Induction

  • Cytoplasmic Determinants: Molecules present in the egg that influence the development of the embryo post-fertilization.

  • Induction Mechanisms: Refers to how nearby cells communicate and influence the developmental paths of adjacent cells.

Fate Mapping of Xenopus Embryos

  • Fate Map Creation: Identifies which blastomeres (cells from early stages of cleavage) become different tissue types in later development.

    • Blastomeres labeled with letters and numbers; e.g., B2 contributes to epidermis and mesoderm.

Heterotopic Transplantation in Embryology

  • Experiments: How transplantation at different developmental stages (early vs. late gastrula) changes outcomes of cell fate for the neural plate.

Reproductive Technologies

  • In Vitro Fertilization (IVF):

    • Definition: The process of fertilizing an egg with sperm outside of the body and implanting the embryo into the uterus.

    • Historical Context: Pioneered by Robert Edwards, recognized with a Nobel Prize in 2010.

    • Statistics: Approximately 20-30% success rate per transfer.

    • First test-tube baby: Louise Brown, born July 25, 1978.

    • Ethical Issues: Concerns around multiple births and the status of unused embryos.

  • Embryo Screening:

    • Karyotyping and DNA Fingerprinting: Techniques used to study embryos for genetic conditions prior to implantation.

    • Pre-implantation Genetic Diagnosis (PGD): Allows testing for genetic diseases before an embryo is used for implantation.

Amniocentesis and Alternatives

  • Amniocentesis: Involves sampling amniotic fluid to obtain fetal cells for genetic analysis.

  • Chorionic Villus Sampling (CVS): Alternative method of prenatal diagnosis that tests cells from the placenta.

Cloning Procedures

  • Step-by-Step Cloning Process:

    1. Identification of donor cells.

    2. Removal of nucleus from egg cell.

    3. Fusion of donor cell nucleus with enucleated egg cell.

    4. Cultivating the fused cell into an embryo.

    5. Implantation into a surrogate mother.

    6. Monitoring embryonic development.

  • Challenges in Cloning:

    • Typically low success rates, issues with health (early aging, other abnormalities).

    • Historical Example: “Dolly”, the first cloned mammal from a mammary gland cell.

Potential Applications of Cloning

  • Therapeutic Cloning:

    • Use of cloned embryos to generate embryonic stem cells for treating conditions (e.g., paralysis).

  • Conservation: Cloning of endangered species to increase population sizes.

  • Organ Production: Developing genetically-engineered organs to reduce risks of rejection in transplant scenarios.

Mammal Cloning Milestones (1997-2007)

  • List of species cloned and their notable years of cloning:

    • Sheep (Dolly, 1997) , Mouse (1998), Cat (2002), Mule (2003), Rat (2003), Bull (1999), Pig (2000), Goat (2000), Wildcat (2004), Dog (2005), Water Buffalo (2005) , etc.

  • Each cloning case noted for its unique circumstances, challenges, or implications for genetics.

Ethical Considerations in Cloning and Genetic Engineering

  • Philosophical Discussions: Engaging with questions like, "Just because we can, should we?"

  • Public Sentiment: Mixed feelings regarding de-extinction and the resurrection of extinct species, illustrated by quotes from bioethicists.

  • Commercialization: The rise and fall of pet cloning companies, exploring market viability and ethical practices.

Stem Cell Research Overview

  • Types of Stem Cells: Distinction between embryonic (totipotent, can be developed from embryos) and adult stem cells (usually multipotent and harder to culture).

  • Stem Cell Applications:

    • Potential treatments for conditions involving damage to cells (e.g., spinal injuries, Alzheimer's). Minimizing risk of cells inducing cancers in patients.

  • Regulatory Landscape: Changes in funding and research practices surrounding stem cell research from the Bush to Obama administrations, leading to evolving ethical debates.