Chapter 8-Specialized cell types can be experimentally reprogrammed to become pluripotet stem cells
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Even more surprising, transcription regulators can coax various differentiated cells to de-differentiate into _____ ______ _____ that are capable of giving rise to all the specialized cell types in the body.
Cultured mouse fibroblasts have been reprogrammed to become ______ _____ stem cells-cells that look and behave like the pluripotent ES cells that are derived from embryos, used to differentiate cells.
Pluripotent stem cells
Induced pluripotent stem cells
Can the formation of an entire organ be triggered by a single transcription regulator?
Whats an example?
Artificially induced expression of the Drosophila Ey gene in the precursor cells of the leg triggers the misplaced development of an eye on a fly's leg.
Give examples of Epigenetic mechanisms that allow differentiated cells to maintain their identity.
- Positive feedback loop.
- DNA methylation
- Modification of histones.
Describe the three steps of positive feedback loop that can create cell memory.
- 1. A signal turns on expression of gene A.
- 2. Protein A then become the transcription regulator that activates the transcription of its own gene.
- 3. Therefore, progenitor cell remembers that a transient signal initiated the production of protein A.
Describe the process of DNA methylation that occurs on certain cytosine bases.
- 1. Formation of methyl group on cytosine by covalent modification.
- 2. Methyltransferase binding to methylated cytosines blocking off gene transcription.
- 3. Methyltransferase copies the methylation pattern on the parent DNA strand to the daughter DNA strand as it is synthesized.
- 4. Maintenance methyltransferase interacts the the double helices and methylates on the CGs that are base paired with other GCs containing the methyl groups.
Describe the histone modifications that may be inherited by daughter chromosomes.
- 1. Parental chromosome with the nucleosomes containing the modified histones.
- 2. Divide.
- 3. Only half of the daughter nucleosomes inherit the modified parental histones, the rest is newly-synthesized not yet modified histones.
- 4. Parent pattern of histone modification is reestablished by enzymes that recognize the same modifications they catalyzed.
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