2017-2018 SAQ Flashcards
List the 4 mechanism establish and maintain the inner cell mass (ICM) in the blastocyst?
a] What mechanisms establish and maintain the inner cell mass (ICM) in the blastocyst?
- Asymetrical Divisions
- Cell-cell signaling
- Cell adhesion molecules
- Transcriptional regulation
1.Asymmetric cell divisions
a] What mechanisms establish and maintain the inner cell mass (ICM) in the blastocyst?
- Early stages of embryonic development
- fertilised eggs divides several rounds> blastocyst forms
- Some divisions:asymmetric
- > leads to 2 distint cell populations
- 1.trophectoderm
- 2.Inner cell mass
- Asymmetric distrubution of cellular components during these divisions helps establishing the ICM
2.Cell-cell signalling
a] What mechanisms establish and maintain the inner cell mass (ICM) in the blastocyst?
- Intercellular communication
- role:establish and maintain ICM
- Cells within ICM: cell signalling interaction for their self-renewal and pluripotent state
Important signalling pathway in ICM
* Fibroblast growth factor (FGF) signalling pathway
* >promote self-renewal of ICM
* Prevents their differentiation
3.Cell adhesion molecules
a] What mechanisms establish and maintain the inner cell mass (ICM) in the blastocyst?
- E-cadherin
- > integrity of ICM
- facilitate cell-cell adhesion and contribute to formation of cohesive ICM structure
Loss of cell adhesion would mean?
* Disrupt ICM
* Leads to differentiation of its cell
4.Transcriptional Regulation
a] What mechanisms establish and maintain the inner cell mass (ICM) in the blastocyst?
- Trancriptional factors
- Epigenetic modifications
- > establish and maintain pluripotent state of the ICM cells
Transcription factors
* Oct 4
* Nanog
* Sox2
* >maintain pluripotent state and repress genes promoting differentiation
Epigenetic modifications
* DNA methlation
* Histone modifications
* >regulate gene expression, maintain pluripotent state
List the 5 roles of the yolk sac development?
b] List the roles of the yolk sac in development
1.Nutrient storage and transfer
2. Blood cell formation
2. Early circulation and oxygenation
3. Extraembryonic membrane formation
4. Germ cell development
- Nutrient storage and transfer
b] List the roles of the yolk sac in development
- Yolk sac
- > provide nutrient to developing embryo
- stores yolk
- > nutrient rich substance absorbed by embryo cells gradually
- > proteins,lipids,vitamins
- > > necessary for early stages of embryonic growth and development
2.Blood cell formation
b] List the roles of the yolk sac in development
- yolk sac involved in production of blood cells during embryonic development
- > Initial site for hematopoiesis (production of blood cells)
- Primitive red blood cells
- some types of immune cells:macrophages produced within
3.Early circulation and oxygenation
b] List the roles of the yolk sac in development
Yolk sac
* responsible for initial circulation of the blood in developing embryo
* Blood vessels in yolk sac faciliate transport nutrients and oxygens->developing tissues
* this stage yolk sac: site for gas exchange(embryo aquire o2 and remove co2)
4.Extraembryonic membrane formation
b] List the roles of the yolk sac in development
- yolk sac
- acts one of the extraembryonic membranes:protect developing embryo
- Along with amnion, chorion. allantois, yolk sac contributes formation of membranes
- > protective environment, regulate fluid balance, aid in waste disposal during development
5.Germ cell development
b] List the roles of the yolk sac in development
Yolk sac
* involved in early development of primordial germ cells,
* >precursor of sperm and eggs
* Germs cells initially migrate from the yolk sac to developing gonads
* >where they undergo further development and differentiation
How do β-catenin-mediated signals contribute to the formationof the amphibian organizer; include a diagram to support your answer.
List the 4 ways
How do β-catenin-mediated signals contribute to the formationof the amphibian organizer; include a diagram to support your answer.
- Dorsal-ventral patterning
- Activation of target genes
- Regulation of Nodal signalling
- Axial mesoderm induction
1.Dorsal-Ventral Patterning
How do β-catenin-mediated signals contribute to the formation of the amphibian organizer; include a diagram to support your answer.
- B-catenin key component of Wnt signalling pathway
- > involved in dorsal-ventral patterning of embryo
- Absence of Wnt signalling, B-catenin target for degradation
- Wnt bind to receptors
- > stabilise and accumulates B-catenin in cytoplasm
- > acting as transcriptional co-activator.
2.Activation of target genes
How do **β-catenin-mediated signals contribute to the formation **of the amphibian organizer; include a diagram to support your answer.
- Nuclear B-catenin forms complex with transcription factors of theT-cell factor/lymphoid enhancer factor (TCF/LEF) family
- > compex binds specific DNA sequences ->promoter regions of target genes>activation
- > inducing TFs and signalling molecules(organiser formation and patterning)
3.Regulation of Nodal signalling
How do **β-catenin-mediated signals contribute to the formation **of the amphibian organizer; include a diagram to support your answer.
- Interacts with Nodal signalling pathway
- > mesoderm induction and organiser formation
- Nodal signals- expression of Nodal-related genes
- > secreted factor Nodal and its antagonist Lefty
- Regulates expression of Nodal antogenist-> restrict Nodal Signalling to the dorsal side of the embryo
- > establising organizer at the dorsal side
4.Axial mesoderm induction
How do **β-catenin-mediated signals contribute to the formation **of the amphibian organizer; include a diagram to support your answer.
- Organizer responsible for inducing for the formation: axial mesoderm structures
- > notochord
- TF Goosecoid and Chordin activated > secretion of Chordin protein
- > antogonize activity of BMP signalling (bone morphogenetic protein)
- > ventralising mesoderm
- how>inhibit BMP,
- > chordin allow dorsal mesoderm to form, including notochord
List the 7 characteristics
List the characteristics that make cleavage a unique form of cell division
- Rapid and synchronous divisions
- Partial cytokineses
- Lack of G1 and G2 phases
- Asynchronus nuclear divisions
- Regulation by maternally derived factors
- No significant cell growth
- Generation of blastomeres
1.Rapid and synchronus divisions
List the characteristics that make cleavage a unique form of cell division
- without significant growth
- resulting daughter cells are smaller
- > efficient partitioning of cytoplasmic contents
2.Partial cytokinesis
List the characteristics that make cleavage a unique form of cell division
- incomplete/partial cytokinesis
What does this mean?
* Daughter cells connected ‘midbodies’/ ‘intracellular bridges’
* >communicated and material exchange
3.Lack G1 and G2 phases
List the characteristics that make cleavage a unique form of cell division
- consist S phase(DNA replication)
- Consist mitosis (nuclear division)
- Absence of G1 and G2
- > allows quick gen of multiple cells
4.Asynchronous nuclear divisions
List the characteristics that make cleavage a unique form of cell division
- nuclie divide at different times within same cytoplasmic mass
- > helps genetic diversity/ diff cell lineage
5.Regulation by maternally derived factors
List the characteristics that make cleavage a unique form of cell division
- Present in oocyte
- cues for initiation and coordinating division by activiating zygotic gene expression
6.No significant cell growth
List the characteristics that make cleavage a unique form of cell division
- Focus on division than growth
