What are stem cells ? - PowerPoint PPT Presentation

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What are stem cells ?

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Title: Development Author: Staff Last modified by: 00, 00 Created Date: 2/16/2004 4:09:57 PM Document presentation format: On-screen Show (4:3) Company – PowerPoint PPT presentation

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Title: What are stem cells ?


1
What are stem cells ?
2
Characteristics that distinguish stem cells from
other cells
  • They are undifferentiated cells (their job is to
    become special cells when needed)
  • They can be grown continuously in a culture (stem
    cell line)
  • They can be changed (using chemicals) to become
    cells with special functions

3
Why the name stem cells
4
Differentiation
  • When a cell becomes a special cell type

What controls differentiation?
  • Chemicals released by other cells
  • The location of the cells (the stem cell niche)

5
Day 14 still the size of a pencil tip
Cells in the blastocyst migrate to form three
layers of cells. Each of these layers are stem
cells, but can only become certain types of
cells. These cells have begun to differentiate.
6
  • All cells have the same genes (information)
  • However, eye cells differ from nose cells
  • So how do they become different?

7
Gene Activation
  • As a cell differentiates, some genes are turned
    on and some are turned off
  • Only the genes necessary to make the type of cell
    needed will be working.
  • Like a computer with all information, but only
    certain programs are turned on, others are off

8
19-26 Days
  • Cells in the embryo continue to migrate and
    differentiate.
  • The brain and spinal cord begin to form.

9
4 weeks1/6 inch
  • By 4 weeks the heart is beating.
  • Cells are still differentiating.

10
5 weeks1/6 inch
11
6-8 weeks ½ inch
12
12-16 Weeks2.5 inches ½ ounce
13
  • Two basic types of stem cells
  • Embryonic stem cells (ESC)-
  • obtained from fertilized eggs left over from
  • in vitro fertilization (IVF).
  • Collected from the inner cell mass (ICM)
  • Original 30 cells yield millions of embryonic
    stem cells
  • Batches of them can be frozen and shipped to
    other laboratories

14
  • ESCs

Scientists have "recipes" of chemicals for the
differentiating ESCs into specific cell types
approx. 30 cells
15
  • Adult stem cells (ASC) -
  • both children and adults have them in specific
    areas (niche)
  • The cells divide and differentiate when needed
  • One cell always remains a stem cell
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