Lecture 2 Flashcards
What are the stages of the life cycle of a frog?
Egg (cleavage) - Morula - Blastula (gastrulation) - Gastrula (neurulation) - Neurula (organogenesis) - Pharyngula/fetus/larva - Juvenile - Adult
What is the general mechanism of fertilization and its role?
Fusion of haploid gametes to form a diploid zygote. The location of the sperm pronucleus with female pronucleus determines the body axe: sperm delivers centrosome which rearrange the egg cytoplasm (cortex rotates).
What is the cleavage step?
Synchronous mitotic divisions where blastomeres (divided cells) end up to surround the blastocoel (fluid filled cavity) of the blastula.
What is MBT?
Midblastula transition: cell divisions become asynchronous and chromatin decondenses. Mother genes contained in the cytoplasm no longer rule the development and you see the zygotic genes starting to be expressed.
What is gastrulation?
The most important step of development. Cells from the outside goes inside the blastocoel, forming the germ layers: ectoderm, mesoderm and endoderm + germ layer.
What are the fates of germ layers generally?
Ectoderm: neurons, neural crest cells and outer surface Endoderm: dorsal, paraxial (bones), intermediate (organ cells), lateral (red blood cells), head (facial muscles) Endoderm: digestive tube, pharynx, respiratory tube Germ layer (form through gametogenesis through meiosis)
What is organogenesis?
Cells communicate with one another and form organs.
1. Cell-cell signaling
2. Migration
3. differentiation
4. Morphogenesis
The first organogenesis is called neurulation.
Describe neurulation. Draw it aside.
It’s the formation of the neural tube from the notochord (mesoderm derived) that rolls into a tube. Then follows the migration of the neural crest.
- Neural furrow
- Neural groove
- Neural folds in contact
- Neural tube formed
- Migration of neural crest
What are the 3 approaches used to study development?
Anatomical
Experimental
Genetic
Give 3 examples of the use of the anatomical approach. Generalize the role of this approach.
Observed the constant development of c. elegans and found the pathway from which cells undergo PCD through apoptosis. Those genes were further studied and they discovered they had a role in cancer.
Mapping of cell fate in the zebrafish embryo using dyes.
Mapping of cell fate using transplantation experiments.
Used to generate hypothesis.
Give an example of the experimental approach. Generalize the role of this approach.
When the Boveris studied wether the nucleus or the cytoplasm was regulating dev. they used this approach in sea urchin: messed up with nucleus content using polyspermy and realized that it was nucleus that was ruling the development.
What are the 2 ways to regulate gene expression?
- Epigenetic control
2. Gene-specific level
What is epigenetic control?
Control of the chromatin state through histone acetylation (open) and methylation (effects vary) or DNA methylation (repress).
What is gene specific control?
Direct control of gene translation. Use of promoters that are gene specific and enhancers that are cell-type specific. Capping, splicing, poly(A) tails, mRNA transport, cap, post-translational modifications are other examples.
What is the genomic equivalence principle?
All cells have the genomic material to form a whole zygote, it is gene expression that will vary across cells of an individual. It is just to do cloning because some reactions are almost irreversible.
