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Cell Potency decreases during development

Cell Potency decreases during development. Totipotent – cell has ability to become any cell type including placenta. Pluripotent – cell has ability to become any cell type EXCEPT placenta.

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Cell Potency decreases during development

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  1. Cell Potency decreases during development • Totipotent– cell has ability to become any • cell type including placenta • Pluripotent – cell has ability to become any cell type EXCEPT placenta • Multipotent– cell fate is restricted, can only become certain types of cells (blood, muscle, skin) • Fully differentiated—can only divide to become same type of cell

  2. A cell’s potency can be measured

  3. Activation of different genes causes differentiation. http://www.readcube.com/articles/10.1038/nature08911

  4. Differential gene expression in a muscle cell

  5. Asymmetric Division – daughter cells born different Symmetric Division – daughter cells born equal, become different as a result of influences after birth Two ways to control cell fate 1. Inheritance of cytoplasmic determinants 2. Induction

  6. 1. Inheritance of Cytoplasmic Determinants • mRNA, proteins, chemicals, and organelles control the fate of the cell

  7. A D V P has anterior/posterior axis and dorsal/ventral axis Body plan of Drosophila 3 main body parts—head, thorax, and abdomen

  8. Cytoplasmic determinants are laid out before the embryo begins cell division. When new cells are formed, they are different, and by step 3, the body plan (axes and segment boundaries) has been established.

  9. Drosophila embryos progressively subdivide into segments

  10. Morphogens (usually transcription factors) control patterns of tissue development based on concentration. Examples: bicoid&nanoscontrol anterior/posterior axis

  11. Homeotic genes (usually code for transcription factors also) determine when, where, and how body parts develop.

  12. Mutations in homeotic genes cause body parts to develop in the wrong places

  13. Homeotic genes are conserved in many organisms. Homeotic genes contain a sequence called the homeobox domain that binds to DNA. In animals, homeotic genes are often called hox genes

  14. 2. Induction by nearby cells Cell-cell signaling directs cell fate. Cells release signal molecules that cause nearby cells to activate certain genes.

  15. C. elegansis a nematode whose entire cell lineage is known. The developmental fate of all 959 cells has been mapped.

  16. A protein secreted from one cell signals one or more target cells, changing their gene expression and causing differentiation. Formation of vulva Formation of intestine

  17. When induction goes wrong… baby worms

  18. Apoptosis (programmed cell death) is important in development. When cell death proteins are activated, proteases and nucleases break down macromolecules in the cell. Cytotoxic T cells use apoptosis to destroy infected or cancerous cells.

  19. Normal white blood cell Apoptotic white blood cell In mammals, interdigital tissue is removed during development by apoptosis.

  20. Stem cells are not fully differentiated • Embryonic stem cells are pluripotent • Adult stem cells are • multipotent Pluripotent Multipotent

  21. Embryonic Stem Cells: Video Video: Howard Hughes Medical Institute http://www.hhmi.org/biointeractive/stemcells/scnt.html

  22. Stem cells as medicine?

  23. Hello, Dolly! (SCNT) • nucleus is from a mammary cell (somatic cell) arrested in cell cycle (Go) • Egg cytoplasm seems to “reset” the mammary cell nucleus • Not very efficient (many embryos die)

  24. Somatic Cell Nuclear Transfer: Video Video: Howard Hughes Medical Institute http://www.hhmi.org/biointeractive/stemcells/creating_lines.html

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