1. What two properties define a stem cell? Distinguish between a totipotential stem cell, a pluripotent stem cell, and a progenitor cell.
2. Where are stem cells located in plants? Where are stem cells located in adult animals? How does the concept of stem cell differ between animal and plant systems?
3. In 1997, Dolly the sheep was cloned by a technique called somatic cell nuclear transfer. A nucleus from an adult mammary cell was transferred into an egg from which the nucleus had been removed. The egg was allowed to divide several times in culture, then the embryo was transferred to a surrogate mother who gave birth to Dolly. Dolly died in 2003 after mating and giving birth herself to viable offspring. What does the creation of Dolly tell us about the potential of nuclear material derived from a fully differentiated adult cell? Does the creation of Dolly tell us anything about the potential of an intact, fully differentiated adult cell? Name three types of information that function to preserve cell type. Which of these types of information was shown to be reversible by the Dolly experiment?
4. The roundworm C. elegans has proven to be a valuable model organism for studies of cell birth, cell lineage, and cell death. What properties of C. elegans render it so well suited for these studies? Why is so much information from C. elegans experiments of use to investigators interested in mammalian development?
5. In the budding yeast ,S. cerevisiae, what is the role of the MCM1 protein in the following?
a. transcription of a-specific genes in a cells b. blocking transcription of a-specific genes in a cells c. transcription of a-specific genes in a cells d. blocking transcription of a-specific genes in a cells
6. In sS. cerevisiae, what ensures that a and a cells mate with one another rather than with cells of the same mating type (i.e., a with a or a with a)?
7. Exposure of C3H 10T1/2 cells to 5-azacytidine, a nu-cleotide analog, is a model system for muscle differentiation. How was 5-azacytidine treatment used to isolate the genes involved in muscle differentiation?
8. Through the experiments on C3H 10T1/2 cells treated with 5-azacytidine, MyoD was identified as a key transcription factor in regulating the differentiation of muscle. To what general class of DNA-binding proteins does MyoD belong? How do the interactions of MyoD with the following proteins affect its function? (a) E2A, (b) MEFs, (c) Id
9. The mechanisms that regulate muscle differentiation in mammals and neural differentiation in Drosophila (and probably mammals as well) bear remarkable similarities. What proteins function analogous to MyoD, myogenin, Id, and E2A in neural cell differentiation in Drosophila? Based on these analogies, predict the effect of microinjection of MyoD mRNA on the development of Xenopus embryos.
10. Predict the effect of the following mutations on the ability of mother and daughter cells of ,S. cerevisae to undergo mating type switching following cell division:
a. loss-of-function mutation in the HO endonuclease b. gain-of-function mutation that renders HO endo-nuclease gene constitutively expressed independent of SWI/SNF
c. gain-of-function mutation in SWI/SNF that renders it insensitive to Ash1
11. Asymmetric cell division often relies on cytoskeletal elements to generate or maintain asymmetric distribution of cellular factors. In ,S. cerevisiae, what factor is localized to the bud by myosin motors? In Drosophila neuroblasts, what factors are localized apically by microtubules?
12. How do studies of brain development in knockout mice support the statement that apoptosis is a default pathway in neuronal cells?
13. What morphologic features distinguish programmed cell death and necrotic cell death? TNF and Fas ligand bind cell surface receptors to trigger cell death. Although the death signal is generated external to the cell, why do we consider the death induced by these molecules to be apoptotic rather than necrotic?
14. Predict the effects of the following mutations on the ability of a cell to undergo apoptosis:
a. mutation in Bad such that it cannot be phosphorylated by Akt b. overexpression of Bcl-2
c. mutation in Bax such that it cannot form homodimers
One common characteristic of cancer cells is a loss of function in the apoptotic pathway. Which of the mutations listed might you expect to find in some cancer cells?
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