1. Stem Cells & Differentiation

2. Cell Specialization
The process by which cells develop from similar cells into cells that have specific functions in an organism.
Cell differentiation: the formation of specialized cells

3. Factors that influence differentiation
Contents of cytoplasm
mitosis = identical nucleus/DNA
cytokinesis does NOT = identical cytoplasm & organelles
cytoplasm contents make cells more likely to specialize for certain functions
example: cells that use a lot of energy need more mitochondria & vacuoles

4. Similar cell conditions = Formation of similar cells
Environmental conditions
cell specialization can be affected by conditions during development
examples:
1. presence/absence of certain nutrients
2. temperature
In Siamese cats, cells that develop at cooler temperatures produce dark hair colours
Similar cell conditions = Formation of similar cells

5. Influence of neighbouring cells
substances produced by one cell can diffuse across cell membrane
may affect how genetic information is expressed (how cell functions)
7-day-old chick embryo
(bluish/black area shows where cells have already begun to differentiate into what will become an eye)

6. Stem Cell
an unspecialized cell that can produce various specialized cells
See figure 3.5 on page 90

7. Types of Stem Cells 1. Totipotent stem cells:
- found in early embryonic
development
- can become any kind of
cell in the body
2. Pluripotent stem cells:
- as embryo develops
- less versatile
- can produce many, but
not all types of cells

8. Types of Stem Cells
3. Multipotent (adult) stem cells: - late in embryo development, at birth and for life - can only produce specific types of cells example: skin stem cells produce cells to repair skin 8

9. Types of Stem Cells

10. Types of Stem Cells 10

11. Classwork: Use of embryonic stem cells
Read page 91 in your textbook (individually) and answer the following questions.
How are embryonic stem cells used in medical research and treatments?
What are some of the ethical issues associated with this practice?
What is the limitation on using adult stem cells?
Then …
In a small group (3-4 students) discuss this topic and try to come to a consensus: Should embryonic stem cells be used for research and treatment?

12. Use of embryonic stem cells
1) How are embryonic stem cells used in medical research and treatments? - treat cancer patients who had radiation therapy (to help restore blood cells) - totipotent stem cells keep dividing for a year or more without ever differentiating - embryonic stem cells are considered “source or starter” cells because they can become about 300 different types of human tissue (valuable for various research & treatments) 12

13. Use of embryonic stem cells
1) How are embryonic stem cells used in medical research and treatments?  test new drugs  cell-based therapies (a renewable source of replacement cells and tissues to treat diseases including Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, and arthritis) 13

14. Use of embryonic stem cells
2)What are some of the ethical issues associated with this practice? - scientists obtain these stem cells from eggs fertilized in vitro (outside the uterus) i.e. unused embryos from fertility clinics - this destroys the embryo (is this taking a human life?) 14

15. Use of embryonic stem cells
3) What is the limitation on using adult stem cells?
- can only produce specific types of cells
- recent studies show that some adult stem cells can be transformed or induced to become pluripotent stem cells (therefore can produce many, but not all types of cells) BUT this is done using viruses which can damage the cell’s DNA
Should embryonic stem cells be used for research and treatment? 15

16. Homework
p. 90 # 1,2
p. 92 # 4 - 8