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Determinant Development

Determinant Development. Chapter 21.2. 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

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Determinant Development

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  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

  9. 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?

  10. 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: http://www.nobelprize.org/nobel_prizes/medicine/laureates/2012/# • http://www.sciencedirect.com/science/article/pii/S0092867406009767

  11. 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

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