Biol 303- Module 3 Flashcards
Differentiation
Process by which unspecialized cells become specialized
Commitment
State in which cell development becomes restricted.
Specification- 3p
- First stage
- capable of differentiating in neutral env
- reversible
Determination- 3p
- Second stage
- irreversible
- differentiate in a non-neutral env
Autonomous Specification - 4p
- Mosaic Dev
- Predominant in most invertebrates
- Differential Acquisition of Morphogenetic Determinants.
- Invariant
Invariant - 2p
- Blastomeres are Invariant
- cells k now their fate without interacting with other cells
Mosaic Dev-
If blastomere is lost embryo doesn’t compensate ny having other cells change fate.
Conditional Specification - 7p
- Regulative dev
- Predominants in vertebrates
- Cell- Cell interaction (Juxtacrine)
- Relative position is key
- Paracrine secreted signals
- Variable cleavage division
- Fate assignment- flexible
Regulative Dev
If blastomere is lost the embryo can compensate.
Transplant
cells can adapt to new env
ablate
surrounding cells adapt/recover structure
Reality of Roux vs Drisech
Embryos can use combination of both autonomous and conditional specification
Driesch vs Roux - 4p each
Roux
1.Mosaic autonomous Dev
2. Hot needle on one side of the blastula
3.The side became dead tissue
4. Half embryo left with one living sides.
Drisech
1. Conditional Regul Dev
2. Removed fertilization envelope
3. Separated 4 cells.
4. Plutei developed from single cells.
Morphogen -
Definition, function, location, diffusion, whats forms, highest conc?
- Form Giver
- Substance that specify cell fates differentially with by their differing concentration.
- Made on specific sites in an embryo.
- Diffuse over long distance
- Form concentration gradient
- Highest conc- point of synthesis.
Syncytium - why does nuclei reside in cytoplasam?
- Many nuclei reside in a common cytoplasm
- Results from karyokinesis (Nuclear division)- without cytokinesis or from cell fusion.
Syncytical Specification -
Interaction,Location
- Interaction of nuclei and Transcriptional factor
- takes place in a common cytoplasm.
Syncytial Blastoder- why like drosophila embryo
- Drosophila Embryo
- No cell membrane exist other than that of the egg itself.
Stages of Syncytial Blastoderm
Stage 1- Newly laid egg
Stage 2- Early Cleavage
Stage 3- Pole cell formation
Stage 4- Syncytial Blastoderm
Stage 5- Cellularization.
Syncytial Specification-Which class uses most?
How body regions specified
Fate?
Specifications after cellularizaton?
- Most insect classes
- Body regions are specified by interactions between cytoplasmic regions prior to cellularization.
- variable cleavage- no rigid cell fates for any particular nuclei- random nuclear distribution
- After cellularization- both auto and conditional specification used.
Bicoid and Caudal are what? importance?
Morphogens, laid down in opposing gradients.
How does syncytial specification work?
- Bicoid and Caudal laid down in opposing gradients
- Syncytial nuclei become distributed evenly through out the cytoplasam
- Location before cellularization determines how much morphogen in each cell.
- combinatorial effect -> specification anterior and posterior body plan.
Fertilization triggers the beginning of embryonic development known as?
Activation
Spermtogenesis
sperm are highly specialized cells.
Haploid nucleus
What replaces histones and why?
Streamlined, DNA tightly compacted,
Protamines, small arginine replace histones- denser packaging of DNA in sperm head.