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14 Cards in this Set
- Front
- Back
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What is the primary driver of cell differentiation? |
Epigenetic modifications/state (eg. methylation, acetylation, etc.) |
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What is evident in differentiated cells compared to un-differentiated? |
Greater density of epigenetic marks. |
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What is the inner cell mass? |
The inner core of the blastocyst - source of embryonic stem cells. |
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What is Somatic Nuclear Transfer? |
A nucleus from a donor cell is transplanted into an enucleated oocyte, and driven to divide. -> can generate ESCs for therapeutic reasons, or cloning |
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Define Heterokaryons. |
Heterokayons result from the fusion of two distinct somatic cells to form a single cell with two nuclei. |
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What are some characteristics of heterokaryons? |
- Cell is a polyploid (extra chromosomes) - Nucleus from the more differentiated cell is often silenced - Trans-acting factors can diffuse between nuclei and reprogram genes. |
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Explain the NCAM stimulation example of heterokaryons. |
Ncam is expressed in mouse cells but not human fibroblasts. -> when mouse and human cells are fused the human cell is inactivated -> NCAM antibodies showed a positive result when inoculated onto the heterokaryon |
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Explain generation of ESCs via fusion. |
Somatic neural cells were fused with ES cells. -> fusion cells were found to have drastically lower CpG methylation and expressed some pluripotency genes |
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What is another method of reprogramming independent of cell fusion? |
Can reprogram somatic cells by localizing them to an environment that promotes de-differentiation. |
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Give an example of ectopic generation of ES cells. |
LacZ transfected neurons were implanted int a mouse embryo. In the developing zygote a random pattern of LacZ expression was observed -> suggest adult neurons were reprogrammed into ES cells. |
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What is the difference between ectopic re-programming, and cell fusion? |
In ectopic reprogramming the donor cell is directly changed into a stem cell, in cell fusion a polyploid cell is created that contains two nuclei, and properties of both cells. |
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When is somatic nuclear transfer more efficient? Why? |
Generally inefficient if using somatic cells, however if using cells from one blastula to another more effective. Epigenetic marks present on differentiated cells are hard to completely abolish. |
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Is the nucleus irreversibly programmed? |
No, the nucleus is amenable to reprogramming under permissive conditions. |
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What causes differential gene expression? |
Reversible epigenetic marks present on the genome of different cells. |
