Bell Ringer Describe each chromosomal disorder: Klinefelter’s Turner’s Downs Syndrome

Gene Regulation  When the sperm and egg meet during fertilization the first cell is called a ZYGOTE  For the first few mitotic divisions the cells are undifferentiated and have the potential to become any type of cell  Genes turn on and off and determine the specialization of future cells  This is called differentiation.

 From the one zygote all of the other cells become specialized to carry out a single functions for that person’s entire life.  Once differentiated they cannot change

Stem cell properties Stem cells are undifferentiated cells (what they are called before they become specialized)  they are capable of dividing and renewing themselves indefinitely  they are unspecialized and undifferentiated  they give rise to specialized cell types

Stem cells  Embryonic stem cells (first few cells after fertilization) also found in the umbilical cord. Ethical issues: the embryo is destroyed in the process  Used in research  Adult stem cells: found in bone marrow and other areas of adults – we are not sure how to turn genes on and off to allow scientist the ability to have them differentiate into any damaged tissue – they seem specific for only the tissue near where they are found,

Regeneration  Planaria could regenerate (grow back) parts because they have stem cells available all of the time.  Other organisms like starfish and some lizards do too.  Human really don’t – our adult stem cells may help regenerate damaged tissue but not to the same extent. Our liver can regenerate, for example.