1. Determinant Development
Chapter 21.2

2. Genomic Equivalence
Genomic Equivalence – all cells have the same genome
Despite genomic equivalence, there are differences in the cells of multicellular organisms
These differences are due to regulatory mechanisms
So although all cells have the same genome, due to differential genetic regulation, they can look and function dramatically differently.

3. Pattern of Development
Development is governed by a combination of cytoplasmic determinants & inductive cell signals
Cytoplasmic determinants
Chemical signals such as mRNA & transcription factors that were distributed unevenly during cleavage
Induction
Interaction among cells that influence their fate
Causes changes in gene expression among cells

4. Totipotent Cells
Cells that are capable of developing into ANY possible cell type
As long as it possesses the requisite genetics, it can become muscular, nervous, epithelial, etc.
If you have a totipotent cell, you can literally grow another organism, and you can grow as many as you would like
Totipotent cells exist until the 16-cell stage of cleavage
After that, they are pluripotent – can become any of the 3 germ layers, but cannot develop into a new being

5. Totipotency in Plants
Plant cells are totipotent throughout their lifetime
Basically plant cloning is easy to do at any stage of development.

6. Totipotency in Animals
Some animal cells could be considered totipotent (kind of), but some were not.
Older nucleus donor = LOWER chance of development
So animal cells change over time in terms of what they can become.

7. Reproductive Mammal Cloning
1997 “born”
2003 euthanized due to respiratory complications usually seen only in older sheep (mom’s age)
Also had arthritis, which is unusual for Dolly’s age, but not for mom’s
Reproductive clones do NOT look like mom or the source of the nucleus.
Clones of mice, horses, cattle, etc have been successful, with defects.

8. Cloning Caturday

10. iPS Cells iPS – Induced pluripotent stem cells
Take an adult (fully differentiated) cell, modify the signaling being received, thus altering the genetic expression of certain “induction” genes
Future of medicine?

11. Dr. Eric Lander’s AMA (2/21/13)
AxelHarver - What do you think is the "coolest" scientific discovery we've made so far in the 21st century?
Eric_Lander[S] - I think Yamanaka's discovery that adult cells can be "reprogrammed" into stem cells was mind-blowing. Completely unexpected. Huge impact.
Nobel Prize in Physiology or Medicine 2012: ne/laureates/2012/#
ii/S

12. Determination
Term used to describe the condition when a cell is irreversibly committed to its fate
Once a cell is differentiated, it expresses genes for tissue-specific proteins
Myoblast
 Determined muscle cell
Differentiation follows determination by MyoD (transcription factor)
MyoD also causes G0 state