stem cells and cell differentiation

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stem cells and cell differentiation
2011-12-01 01:51:22
biology stem cells

biology 160
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  1. stem cells
    • immature cells that can divide and differentiate into specialized cell types
    • most body tissues contain stem cells that help regenerate those tissues and organs
  2. stem cells to build new organs
    • biopsy of the organ tissue is taken from the patient
    • the stem cells form each tissue are grown in culture, allowing the cells to divide and create large numbers of cells
    • the stem cells are layered onto a biodegradable scaffold in the shape of the organ, and the scaffold is placed in a chamber with nutrients and chamicals to support and encourage cell growth
    • surgeons implant the newly grown organ into the patient's body
    • tissues grown from a person's own cells pose no risk of rejection because the tissue is genetically related to the donor
  3. cell differentiation
    • specialized cells express different genes
    • every cell in a person's body contains the same genes, or genome, but each type of cell has a unique pattern of gene expression. each type of cell makes a unique set of proteins and has a unique function in the body
  4. cullular differentiation
    process by which a cell specializes to carry out a specific role
  5. differential gene expression
    process by which genes are "turned on" (expressed) in diferent cell types
  6. embryonic stem cells
    stem cells that make up an early embryo, which can differentiate into nearly every cell type in the body
  7. adult stem cells (somatic stem cells)
    stem cells located in tissues that help maintain and regenerate those tissues
  8. multipotent
    describes a cell with the ability to differentiate into a limited number of cell types in the body
  9. pluripotent
    describes a cell with the ability to differentiate into nearly any cell type in the body
  10. totipotent
    describes a cell with the ability to differentiate into any cell type in the body
  11. regenerative medicine
    • seeks to manipulate stem cells into cell types that they wouldn't differentiate into on their own
    • drawback to engineering new organs is that sugeons have to operate on the patients to obtain stem cells and again to repair the damaged organ
    • would allow damaged organs to be repaired from within by stimulating stem cells to divide and differentiate when they otherwise would not
    • cells in the body continuously divide to replace damaged or aging cells
    • can use therapeutic drugs to stimulate specific stem cells in the body to grow and differentiate
    • can also involve removing stem cells from the body, chemically inducing them to reproduce and differentiate, and then re-implanting a small sample of differentiated cells into a patient with a damaged tissue or organ
  12. differences in stem cells
    • embryonic stem cells are found in the blastocyst stage (the stage of embryonic development in which the embryo is a hollow ball of cells) of an early embryo
    • depending on the stage of embryonic development embryonic stem cells may be either totipotent or pluripotent
    • embryonic stem cells have more developmental flexibility, so some scientists argue that they hold greater potential in treating disease
    • embryonic stem cells can be obtained from 1. discarded embryos from fertility clinics 2. cloning
  13. somatic cell nuclear transfer
    • also known as cloning
    • scientists replace the nucleus of a haploid unfertilized human egg with the diploid nucleus taken from another cell, creating a new embryo with the same genes as the donor cell
  14. US policies on cloning
    • reproductive cloning is illegal - implantation of cloned embryo into a woman's womb, which would develop into a fetus that has the same nuclear DNA as the person who donated the diploid cell
    • therapeutic cloning is allowed - creation of cloned embryos for research
  15. obtaining embryonic stem cells
    • regardless of origin, removing the embryonic stem cells destroys the embryo
    • many people find embryonic stem cell research ethically troubling and raises many moral and ethical issues
  16. induced pluripotent stem cells (iPS cells)
    • pluripotent stem cell that was generated by manipulation of a differentiated somatic cell
    • skin cell (fibroblast) -> other cell types
  17. antibiotics
    chemicals that either kill bacteria or slow their growth by interfering with the function of essential bacterial structures
  18. antibiotic resistance
    • bacteria can acquire resistance
    • mutations when their DNA replicates during reproduction via binary fission
    • antibiotic resistance genes via conjugation
  19. binary fission
    • type of asexual reproduction in which one parental cell divides into two
    • single parental cell simply replicates its single chromosome, grows in size, then splits into two daughter cells, each with a copy of the parental DNA
  20. population
    group of organisms of the same species living together in the same geographic area
  21. evolution
    change in allele frequencies in a population over time
  22. fitness
    • the relative ability of an organism to survive and reproduce in a particular environment
    • the greater an organisms fitness, the more likely that alleles carried by that organism will be passed on to future generations and increase in frequency
  23. adaptation
    response of a population to environmental pressure, so that advantageous traits become more common in the population over time
  24. natural selection
    differential survival and reproduction of individuals in response to environmental pressure that leads to change in allele frequencies in a population over time
  25. directional selection
    a type of natural selection in which organisms with phenotypes at one end of a spectrum are favored by the environment
  26. stabilizing selection
    type of natural selection in which organisms near the middle of the phenotypic range of variation are favored
  27. diversifying (or disruptive) selection
    type of natural selection in which organisms with phenotypes at both extremes of the phenotypic range are favored by the environment
  28. stopping superbugs
    because the use of antivbiotics can drive bacterial populations to evolve resistance, antibiotic resistance is inevitable. the best way to control resistance is to change practices that enable resistant strains to thrive