Oogenesis (wk1) Flashcards
Why is it hard to study mammalian embryogenesis?
E.g. mice= only produce a couple of eggs
Where as sea urchins produce millions
What are oogonia?
Self renewing stem cells
Give rise to oocytes (once they reach the last mitotic division)
Diploid
Often form as clusters= protection
Kept outside the embryo early on and then migrate to the gonad so that they aren’t contaminated by other differentiating factors from different cell types
In a pluripotent state
What are oocytes and differentiate between primary and secondary
Enter meiosis to become haploid
Primary= until completion of the first meiotic division
Secondary= until completion of the second meiotic division
Define oogenesis
Prolonged process of cell interactions between the oocyte and its somatic accessory cells
Define gonad
organs with germ lines cells and somatic cells
List the major developmental changes in egg development
- Transition from mitotic stem cell to a meioticly commited egg precursor
- Transition to vitellogenesis from slow growth to a period of rapid accumulation of nutrients
- Completion of meiotic divisions resulting in a haploid genome
Define differential gene expression and morphogenetic determinants
Differential gene expression= starts in egg development and often results in the presence of morphogenetic determinants in the egg cytoplasm
Morphogenetic determinants= factors in regions of the mature eggs that have important roles in development
Describe some methods in the lab used to determine oogenic cycles
Direct anatomical observation of ovary maturity
Histology/histochemistry
Immunocytochemistry
Molecular biology/in situ hydbridization
Compare the longevity of oogonia in different species
Sea urchins/frogs/fish= oogonia are self renewing stem cells, endure for the adults life time, generate new cohorts each year
Mammals= oogonia divide to form a limited number of egg precursor cells, no ability to regenerate, females eventually run out of eggs
When do the germ cells begin active proliferation in humans?
Week 12-16 of development
T/F: the mammalian female germ line begins in embryonic life and the egg enters and remains in telephase
False
the egg enters and remains in prophase
Define attrition and follicular attrition
Attrition= extensive process of germ cell death
Follicular attrition= when germ cells are lost after death of the supporting follicle cells in an event called follicular atresia
List some factors that are accumulated in the egg necessary to support its growth
Nutrients
- Vitellogenin
- Yolk
- Lipids
- Carbohydrates
- Protein
mitochondria
RNA/DNA
T/F: the perivitelline space is found between the plasma membrane and the zona pellucida
True
Define the two phases of egg development in animals: previtellogenic phase and vitellogenic-lipogenic phase
Previtellogenic phase= increase in number of ribosomes to support protein synthesis, increase in mRNA in the cytoplasm
Vitellogenic-lipogenic phase= deposition of nutrients
e.g. vitellogenin, lipids (triglyceride, chloesterol)
Describe the levels of yolk and size of a variety of species
Birds= lots of yolk/lipid, massive single cell egg Fish= vary in size Mammals= less yolk due to the presence of the placenta, really small eggs
