Cellular Mechanisms of Development Flashcards
Development
Gene directed changes of an organisms life cycle
4 sub-processes in development
- Cell division
- Differentiation
- Pattern Formation
- Morphogenesis
fertilization
process forms diploid zygote or the union of haploid egg + sperm
What happens after fertilization
diploid zygote undergoes rapid mitotic division or cleavage
What is the cell cycle and where does rapid mitotic division occur
G1, G0, S, G2, mitosis (mitotic division), cytokinesis
What is the cell cycle controlled by? Explain in general.
Cell cycle is controlled by proteins: cyclins, cyclin dependant kinases. They control timing and the number of cell divisions
Role of cyclin and cyclin-dependant kineses in adult cells and embryonic cells
adult cells: they control the cycle of mitosis through checkpoints (3, G1, S, G2)
Embryonic cells: inactivation and degradation of kinases allows cell to complete mitosis
what is the difference between the cell cyle of adult and embryonic cells
adult cells: 3 cyclin proteins are active, G1 and G2
Embryonic cells: 1 cyclin protein is active, NO G1 and G2 so shorter, cyclin degradation required to complete mitosis
Cleavage and in mammals
Rapid cell division
after fertilization, zygote divided in smaller cells called blastomeres
In mammals: several days, produces a ball of cells called blastocyst or blastula
Steps from fertilization to blastula
fertilized egg, 2-cell stage, 4-cell stage, 8-cell stage, morula (compact mass of cells, zygote with many cells, size doesnt change), blastula (hasnt grown but hollow), early gastrula, gastrula
egg first divided in 2 blastomeres, then 8 and more blastomeres
What does blastocyst or blastula made of
- Trophoblast: outer layer to form placenta
- Inner cell mass source of embryonic stem cells
- Empty space called blastocoel
Stem cells
cells capable of continued division, that can also give rise to differentiated cells (we can keep them forever, they have not differentiated yet)
Recap, sperm-egg to human embryo and when are stem cells set aside
sperm cell and egg cell join, cell cleavage produces blastocyst, inner cell mass develops into human embryo
embryonic stem cells isolated from inner cell mass and continues to divide while remaining undifferentiated
types of embryonic stem cells and where they are found
- Totipotent: can give rise any cell type in organism, in total zygote
- pluripotent: can give rise many different cell type, in inner cell mass
- Multipotent: can give rise limited # cell type, in many organs: specialization potential limited to 1 or more cell lines
* Unipotent: can give rise 1 single cell type
Where are plant stem cells found and in what do they differentiate in
Meristems, they continually divide and differentiate into leaves, roots, branches and flowers.
In plants, in what are totipotent cells found in
Roots, leaves, shoots from undifferentiated cells
Do animal cells have to move for normal development?
Yes, this cell movement is called gastrulation
Do plant cells have to move for normal development?
No, they only change orientation of cell division to control cell proliferation
Gastrulation allows formation of 3 germ layers, whihc one will become the digestive system
ectoderm, mesoderm, endoderm (this one)
What name is given to the cells that divide rapidly inside the embryo?
Blastomeres
What is the name that an early embryo receives on Day 4 of development?
Morula
Explain how the blastocoel is formed during blastulation; name the layer of cells on the outside and the inside the blastocyst
The blastomeres are nourished by uterine milk going through the zona pellucida. The blastomeres keep dividing and the increase in uterine milk in the morula forms a fluid-filled cavity called blastocoel. The outer cell mass of the blastocyst is called the trophoblast and the inner cell mass is called the embryoblast.
On the third week of development, what important embryonic process occurs that allows to form the three (3) germ layers?
Gastrulation
What is the role of the primitive streak in gastrulation?
The primitive streak allows the cells to move from the outside to the inside of the blastocyst and form the three germ layers.