chapter 8 - early development in invertebrates the next chapters examine early development in...
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Chapter 8 - Early Development in invertebrates
• The next chapters examine early development in several models, including invertebrates (Ch. 8-9) amphibians (ch 10) and then vertebrates (ch. 11)
1 frog egg becomes ______ cells in __ hours!
Fig. 8.1
1. _____- One cell is subdivided into many cells to form a blastula
2. ___________- Extensive cell rearrangement to form endo-, ecto- and meso-derm
3. ___________- Cells rearranged to produce organs and tissue
4. ________________- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells
General Animal Development
Recall from lecture 1
How does egg undergo cleavage without increasing it’s ____?
• Answer- it abolishes ___ and ___ phases of ________.
• Do you need a cell cycle primer??
Four cell cycle phasesM- _________G1- __________- DNA Synthesis___- Gap 2
a. Cleavage
Reminder- mitosis occurs in __ phase, DNA replication in ____________
From Mol. Biol of the Cell by Alberts et al, p864
a. Cleavage
• _________________ (cdk, cdc) drive the cell cycle• But ________ (e.g cyclin A, B…) regulate cdk (cdc) activity
______________________________ (MPF= cyclin B+cdc2)
Example-
MPF
a. Cleavage
Again, how does egg undergo cleavage without increasing it’s size?
• Answer- it abolishes __ and___ phases of cell cycle
Cyclins are _________ in
eggs
Cyclins are _________
S phase
M phase
a. Cleavage
What actually drives the _______ process?
Answer- Two processes-
1. _________________ (mitotic division of the nucleus)
• The mitotic spindle (microtubules composed of tubulin) does this
2. __________ (mitotic division of the cell)
• ___________ “pinch off” (microfilaments composed of actin) Fig. 8.3
_____________ prevents cytokineses
a. Cleavage
1. Cleavage- One cell is subdivided into many cells to form a blastula
2. __________- Extensive cell rearrangement to form endo-, ecto- and meso-derm
3. Organogenesis- Cells rearranged to produce organs and tissue
4. Gameteogenesis- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells
General Animal Development
Recall from lecture 1
Gastrulation- cells of blastula are dramatically _______________• Three germ layers are produced
Five types of _____________
1 2 3
b. Gastrulation
GastrulationFive types of movements
4 5
b. Gastrulation
Axis formationThree axes must be determined-
• ___________________ (head-tail)• ________________ (back-belly)• ______________ (right side-left side)
Fig. 8.7
b. Gastrulation
Now let’s take a look at one beast- the ____________
• Cleavages 1 and 2 are through ______________ poles
• Cleavage 3 results in four ________ and four ______cells
1 2
3
Fig. 8.8
• Cleavage 8 _______ (animal pole) plus 4 _________ and 4 ____________ (vegetal pole)
4
1. Cleavage
• Post cleavage 5Fig. 8.9
Cell fate map
_______________ signal other cells via to influence fate
• Micromere cell fate is _____________- these become ____________ tissue if placed in a dish
• All other cells have ____________specification
Example- Transplant micromeres to animal pole at
___________ stage
•Micromeres cause a second __________•Animal pole cells become _______cells
Fig. 8.13
Sea urchin (continued)
EggLate
_______
________
Later stages
Fig. 8.16 Sea urchin development
2. Gastrulation
Note-micromeres produce ______
_________ which will become larval _______
How do __________ cells know to migrate inside
________?
Answer- changing cell ________________
___________
Extracellular matrix
Basal _____
Primary __________ cell
___________
98% decrease in ________ affinity100-fold increase in _____________ affinity
Fig. 8.19
How does __________ occur?Terms- •Invagination region is called _________•Opening created is called the ___________
Answer- swelling of inner _______ layer
Inner layerOuter layer
_______ cells secrete chondroitin sulfate proteoglycan, causing inner layer to swell and cause _________
________
Now let’s take a look at another creature- the nematode C. elegans
• ___cells at maturity• ____ long• Produces eggs and sperm (___________)• Transparent• __ hours from egg to hatch• Entire genome sequences- ___________ genes
What a great model!
1mm
Mature eggs passes through the ________ on the way to the _______
Germ cells undergo ______,
then begin meiosis as travel down _________
Oviduct
Cleavage
C. elegans
1. Cleavage
1. Cleavage
• Cleavages 1 produces _______ cell (AB) and ______ cell (P1)
• Cleavage 2 results in three _______ cells and one ______ cell (P2)
1 2 3
• Remaining cleavages result in a __________ cell and more founder cells
Fig. 8.42
C. elegans
How is the ___________________ axis determined? Answer- ___________- ribonucleoprotein complexes
•________ always stay associated with the “P” cell
Fig. 8.43
C. elegans
1
3
5
•____ proteins- these specify ______, cell ________ and cytoplasmic __________.
What directs the __________?
C. elegans
1. Cleavage
• P1 develops ________________
• AB does not (thus is ____________)
What drives P1 lineage?P granules? No, these do not enter ________!
Other possibilities• _____- a bZIP family transcription factor that control
EMS cell fate• ______ - a transcription factor required for P2 lineage• ______- inhibits SKN-1 and PAL-1 in P2
Yes- P2 produces a signal that tells ABp to only _______ and ________ cells, not pharynx like ABa
• _____ is the receptor on ABp, and _____ is the ligand on P2
GLP-1 is a ____family proteinAPX-1 is a _____family protein
Does P2 dictate fate of _________ cells?
An example of _________ signaling
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