replacements for terminally differentiated cells are generated from a stock of proliferating precursor cells that derive from a small number of dividing stem cells -not terminally differentated and can divide without limit, when a stem cell divides it can either stay a stem cell or can become differentiated
What is genomic equivalence?
all cells have the same genome, cells only express a small portion of the genome
Describe how you might demonstrate regulative development
driesch's demenstration: intact 4 cell sea urchin embryo generates a normal puteus larva, when you remove the 4-cell embryo from fertilization envelope and isolate each of four cells each can form smaller, but normal, pluteus larva (the larvae are not identical, despite ability to generate all the necessary cell types)
What is SCNT?
somatic cell nuclear transfer, nuclear reprogramming take adult from culture skin cells, pipette nucleus into denucleated unfertilized egg, develops into a normal embryo and tadpole
What does the cloning of Dolly tell us?
mammalian somatic cell nuclei are totipotent, cells from adult tissue can be used for cloning (reproductive cloning)
What are the differences between reproductive and therapeutic cloning?
reproductive cloning: cloning of an entire multicellular animal, achieved through nuclear transplantation, this can give rise to a an early embryo that is put into uterus of foster mother -therapeutic cloning: cloning of cells, a single epidermal stem cell from skin and let it grow in culture to obtain a large clone of genetically identical epidermal cells
What is asymmetric cell division?
often seen in more basal life forms (worms, amphibians etc)--partially or terminally differentiated cells revert back to an earlier developmental stage, usually as a part of regenerative process
stem cell can give rise to all cells of an organism, embryonic and extra embryonic cells (fertilized egg)
stem cell can give rise to all the cells of the mebryo (ectoderm, mesoderm, endoderm and germ cells) but not to the extra embryonic cells trophoblasts of the placenta (ES cells)
stem cell can give rise to only a limted number of somatic cell types (ex HSC)
stem cell can only give rise to a single cell type (ex: SSC)
Describe the Xenopus laevis totipotency experiment
took enucleated egg from WT frog, donor nuclei from female tadpole with albino parents, all the progeny were albino and female -totipotency of nuclei decreases as development proceeds
what is HSC?
hematopoetic stem cell, multipotent stem cell that can self renew and differentiate into all the blood cells
What is a stem cell niche?
stem cells dont function alone but are dependent on their microenvironment and signaling (niche), extracellular signals coordinate cell proliferation, growth, death and differentiation
What type of stem cell is in the gut?
multipotent stem cells, renewal occurs continuously in the lining of adult intestine, stem cells throughout, interspersed between other differentiated cell types
what is the role of Wnt in gut crypts?
signal molecules that keep the stem cells and precursor cells at the base of intestinal crypt in a proliferative state, helps control the production of differentiated cells from a stem cell in the intestine
What is the basal lamina?
The ventral plate of the embryonic neural tube that gives rise to somatic and visceral motor neurons. (not sure if this is right)
What is an SSC?
spermatogonial stem cells: the seminiferous tubules of the adult mammalian testis contains true SScs
How can stem cells be used in regenerative medicine?
ES cells derived from an embryo can give rise to all of the tissues and cell types of the body, can be maintained indefinitely in culture, if they are put back into an embryo they will integrate perfectly and differentiate to suit whatever environment they are placed in, they can also be kept in culture and supplied with different hormones or growth factors to encourage them to differentiate into specific cell types
Can you use adult cells to get pluripotent stem cells?
yes- induced pluripotent stem cells (iPS) can be generated by direct transformation of cells from adult tissues, take cells from an adult tissue and put them in culture, using genetically manipulated viruses as vectors they introduce artificial versions of a specific set of genes coding for transcription regulators that are normally expressed in ES cells, drive production of corresponding proteins
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