CVA Biology I - B10vrv3104

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CVA Biology I - B10vrv3104

  1. 1. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationLesson OverviewLesson Overview10.4 Cell Differentiation10.4 Cell Differentiation
  2. 2. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationTHINK ABOUT ITThe human body contains hundreds of different cell types, and everyone of them develops from the single cell that starts the process. Howdo the cells get to be so different from each other?
  3. 3. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationFrom One Cell to ManyHow do cells become specialized for different functions?
  4. 4. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationFrom One Cell to ManyHow do cells become specialized for different functions?During the development of an organism, cells differentiate into many typesof cells.
  5. 5. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationAll organisms start life as just one cell.Most multicellular organisms pass through an early stage of developmentcalled an embryo, which gradually develops into an adult organism.
  6. 6. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationDuring development, an organism’s cells become more differentiated andspecialized for particular functions.For example, a plant has specialized cells in its roots, stems, and leaves.
  7. 7. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationDefining DifferentiationThe process by which cells become specialized is known asdifferentiation.During development, cells differentiate into many different types andbecome specialized to perform certain tasks.Differentiated cells carry out the jobs that multicellular organisms needto stay alive.
  8. 8. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationMapping DifferentiationIn some organisms, a cell’s role is determined at a specific point indevelopment.In the worm C. elegans, daughter cells from each cell division follow aspecific path toward a role as a particular kind of cell.
  9. 9. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationDifferentiation in MammalsCell differentiation in mammals is controlled by a number of interactingfactors in the embryo.Adult cells generally reach a point at which their differentiation iscomplete and they can no longer become other types of cells.
  10. 10. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationStem Cells and DevelopmentWhat are stem cells?
  11. 11. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationStem Cells and DevelopmentWhat are stem cells?The unspecialized cells from which differentiated cells develop are knownas stem cells.
  12. 12. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationOne of the most important questions in biology is how all of the specialized,differentiated cell types in the body are formed from just a single cell.Biologists say that such a cell is totipotent, literally able to do everything,to form all the tissues of the body.Only the fertilized egg and the cells produced by the first few cell divisionsof embryonic development are truly totipotent.
  13. 13. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationHuman DevelopmentAfter about four days of development, a human embryo forms into ablastocyst, a hollow ball of cells with a cluster of cells inside known asthe inner cell mass.The cells of the inner cell mass are said to be pluripotent, which meansthat they are capable of developing into many, but not all, of the bodyscell types.
  14. 14. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationStem CellsStem cells are unspecialized cells from which differentiated cellsdevelop.There are two types of stem cells: embryonic and adult stem cells.
  15. 15. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationEmbryonic Stem CellsEmbryonic stem cells are found in the inner cells mass of the earlyembryo.Embryonic stem cells are pluripotent.Researchers have grown stem cells isolated from human embryos inculture. Their experiments confirmed that embryonic stem cells have thecapacity to produce most cell types in the human body.
  16. 16. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationAdult Stem CellsAdult organisms contain some types of stem cells.Adult stem cells are multipotent. They can produce many types ofdifferentiated cells.Adult stem cells of a given organ or tissue typically produce only thetypes of cells that are unique to that tissue.
  17. 17. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationFrontiers in Stem Cell ResearchWhat are some possible benefits and issues associated with stem cellresearch?
  18. 18. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationFrontiers in Stem Cell ResearchWhat are some possible benefits and issues associated with stem cellresearch?Stem cells offer the potential benefit of using undifferentiated cells to repairor replace badly damaged cells and tissues.
  19. 19. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationFrontiers in Stem Cell ResearchWhat are some possible benefits and issues associated with stem cellresearch?Stem cells offer the potential benefit of using undifferentiated cells to repairor replace badly damaged cells and tissues.Human embryonic stem cell research is controversial because thearguments for it and against it both involve ethical issues of life and death.
  20. 20. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationPotential BenefitsStem cell research may lead to new ways to repair the cellular damagethat results from heart attack, stroke, and spinal cord injuries.One example is the approach to reversing heart attack damageillustrated below.
  21. 21. Lesson OverviewLesson Overview Cell DifferentiationCell DifferentiationEthical IssuesMost techniques for harvesting, or gathering, embryonic stem cellscause destruction of the embryo.Government funding of embryonic stem cell research is an importantpolitical issue.Groups seeking to protect embryos oppose such research as unethical.Other groups support this research as essential to saving human livesand so view it as unethical to restrict the research.

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