Flashcards in W3 Deck (27):
What is self-renewal?
Stem cells can go through a number of divisions without changing their identity.
What is differentiation?
SC of daughter is set on a path of differentiation, are able to renew and may still be able to change it's fate.
What are some aspects of terminally differentiated cells?
The are usually unable to self-renew.
Differentiation cannot be altered.
What are "knock-out mice"?
Genetically engineered mice using stem cells.
What technique was used to generate Dolly?
SCNT (somatic cell nucleus transplantation into oocyte)
What are the steps of zygote formation?
1. sperm fuses with mature oocyte which is arrested at second meiotic divisions.
2. Sperm fusion triggers completion of meiosis and the zygote is formed.
Describe the pronuclear stage.
Maternal and paternal pronucleus (haploid) are still separate. They migrate and become closely opposed.
What are the stages after fertilization?
1. - 2, 4, 8 cell stage
What are the parts of the blastocyte and what do they form?
1. outer layer - trophectoderm - forms extra-embryonic tissue (placenta)
2. blastocoel (fluid filled)
3. Inner cell mass (ICM) - becomes the new animal.
What does gastrulation develop.
3 germ layers
ectoderm, mesoderm, endoderm
used to evaluate to what extent the development fate has already been specified.
1. cells removed
2. placed in in vitro culture
3. see what type of cells are developed.
What embryological approaches are used to analyse the restriction of development potency?
1. fate mapping
2. isolation experiments to analyse specification
3. transplantation expriments to analyse determination
What is induction?
The influencing of development fate by signals from another cell or cell group.
Spermann and Mangold experiment.
replaced implanted extra dorsal lip in blastospore. frog with 2 spinal cords developed.
What are the stem cells in bone marrow?
multipotent hematopoietic stem cells.
1. bone marrow -
2. bone marrow produces blood
3. some blood cells produce tissues
What is Weismann's theory of nuclear determinaiton?
factor in the cell which drive determined development are unevenly distributed during cleavage. These factors correspond to genes.
SCNT shows that this is wrong.
What was the process by which Dolly was cloned?
Oocytes taken from oocyte donor (scottish Blackface) Nucleus removed.
2. Udder cells taken from genome donor, grown to stage G1, transferred to enucleated egg.
Egg starts embryogenesis. After 7 days implanted into foster mother.
What are some problems with cloning with SCNT?
Not perfect clone because mitochondria DNA come from Oocyte mother.
Also difficult to reprogram already programmed DNA.
What happens when undifferentiated ES cells are injected into mouse?
How are knock-out mice generated?
a. ES cells cultured and
b. modified gene added to one cell (HoxA10 modified by adding neor gene. Homologous recombinateon. Heterozygous cell selected.
c. and injected into blastocyst. Blastocyst implanted in uterus. Chimeric mice generated.
d. breed chimeric to wild tipe. one wild type and two heterozygote offspring. Heterozygote offspring produce one wild type, one homozygote and one heterozygote.
What factors are responsible for the pluripotent state of ES cells?
Oct 4 and Nanog well correlated with pluripotency.
What factors explain the stability of determined/differentiated cells?
1. positive feedback loops by transcription factors
2. epigenetics (propagation of DNA modifications and/or histone modifications) seen in deactivated X chromosome.
cell-intrinsic and cell-extrinsic regulation.
Cell-intrinsic: Asymmetric protein localization determines different fates of daugher cells. (e.g. Drosophila Neuroblasts)
cell-extrinsic: Niche signals determine different fates of daughters. (e.g. Drosophila Germline steem cells)
Niche in Drosophila ovary development.
CC: cap cells form niche for Germ Line Stem Cells. Provide Dpp
GSC: divide in polar fashion. cell with contact to CC stays GSC, other cell becomes Cystoblast (CB)...
What can be used to detect mRNA?
in situ hybridisation
What can be used to detect proteins?