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.
Name the three structures that are formed during Neurulation
Neural plate, neural tube and neural crest
steps early embryogenesis
fertilization (fusion egg-sperm), cleavage (rapit mitotic div), gastrulation (mvt cells to form 3 germ layers), neurolation (neural plate, tube, crest), embryonic folding
What is cell differentiation and why does it happen
Cell differentiation=cell fate (cell undergoes changes to make plan happen) due to differential expression of genes
Which types of cells have been used to study differentiation and what cells do they give rise to
Human pluripotent stem cells give rise to types of blood, cardiac muscle and neural cells
What comes before differentiation, explain
determination: molecular decision to become particular type of cell or cell commits particular developmental pathway (cell determined to become something specific)
What are 2 de developmental pathways in cell determination
cytoplasmic determinants (pigment granules act as cd and detremines the cells fate) and cell to cell interactions or induction (cells from germ layer receives chem signal (FGF factor) from cells found in another germ layer to induce diff cell types
What happens to cells when not determined vs determined
during dev, cells moved to diff location in embryo. If they dev according to new position they are not determined (didnt have plan yet)
Why can cloning occur based on cell differentiation
de-differentiation
how does cloning occur
1 or more organism genetically identical to parent that donated single cell.
what type of cell can generate a complete new organsim
Totipotent
what is the frog embryo experiment
less differentiated cell in egg with donor nucleus
- most develop in tadpoles
- older donor nucleus results lower% normal dev
what did dolly the sheep show, and what process was used on her
differentiation in animals is reversible
somatic cell nuclear transfer (from fully differentiated cell) (mammary cell fused with extracted egg cell by electric shock)
problems of reproductive cloning
low success rate
age associated disease
lack of imprinting (not enough time to reprogram)
nuclear reprogramming and 3 ways
reprogram adult cells to become pluripotent
1-fusion of es cells to differentiated somatic cells
2-culture of germ cells and adult stem cells after long time in culture
3-use specific transcription factors
Steps of therapeutic cloning
isisi 1-isolate skin cell 2-scnt 3-insert nucleus of skin cells in enucleated eggs 4-blastocyst grows 5-get rid embryo and use stem cells 6-stem cells induced to grow any tissue
difference therapeutic cloning and reproductive cloning
see notes but same begining (theraapeutic take nucleus from diabetic patient), but therapeutic cloning instead of implantic blastocyst in uterus to have healthy cloned baby, the embryonic stem cels are grown in culture and implanted
what is allowed in terms of cloning
stem cell reaearch in unimplanted embryos
what 2 genetic pathways control the establishment of polarity in drosophilia
bicoid and nano proteins (anterior/posterior) and dorsal proteins (dorsal/ventral), they activate genes for formation body structures
an example of master regulatory gene that when activated determines a structure
Hox genes, gene that controls development of particular body part
predominant homeotic gene family in plants
MADS-boxgenes: for root and floral development
stages of early embryogenesis
fertilization, cleavage, gastrulation, neurulation, embryonic floding and organogenesis
what happens after cleavage
rate of ell division slows and normal cell cycle restored
Morphogenesis
process by which cells occupy appropriate location: includes gastrulation (mvt cells from surface to interior embryo) and organogenesis (formation of organs)
Gastrulation
rearranges cell, by mvt from surface to interior, into 3 layered embryo called gastrula: ectoderm-endoderm-mesoderm
3 germ layers and where
ectoderm: outer layer
endoderm: lines digestive tract
mesoderm: partly fills space between ectoderm and endoderm
programmed cell death
cells shrivel and shrink during apoptosis: planned through genetic control
