Topic.2.Development.powerpoint.2.3.Developmental.mechanisms Flashcards
What are the two mechanisms underlying development?
Cytoplasmic determinants
signaling molecules
What are cytoplasmic determinants?
Maternal substances in the egg that influence gene expression in a localized area
Ex: mRNA encoding transcription factors,
How do signaling molecules influence development?
Signaling molecules from neighboring cells
Ex: certain signal molecules cause specific changes in gene expression sending the cell down a specific developmental path
Cells make developmental decisions by responding to
___ in their internal ___. They make developmental decisions within a __ and __ framework.
signals, local environment
temporal, spatial
What is the mechanism underlying development in P granule localization in c.elegans?
Cytoplasmic determinants
P granules are complexes of RNA and protein
Initially distributed throughout zygote but are repositioned to posterior end of zygote, found in P4 blastomere which gives rise to gametes.
Essentially p granules being localized to one area, categorize those cells fate of being gametes
Give me two example that show how the body plan is predetermined in frogs?
Frog:
A/P determined during oogenesis
D/V determined at fertilization
What is the evidence that shows frogs A/P was determined during oogenesis?
Dark melanin granules found in animal hemisphere
Yolk in vegetal side
What is the evidence that shows frogs D/V was determined during fertilization?
Cortical rotation: plasma membrane rotates toward the point of sperm entry, which enables molecules in parts of the vegetal cortex to interact with molecules in the animal cortex leading to specific gene expression
What evidence gives rise to the body plan in chicks before fertilization?
A/P axis may begin to be established by gravity as the
eggs moves down oviduct
What is the other evidence that gives rise to body plan in chicks?
pH differences between the two sides of the blastoderm
cells lead to D/V patterns
What creatures are a good example of pattern formation?
Pattern formation: the development of a spatial organization in which the tissues and organs of an organism are all in the right place.
Insect: Axis formation
Often involves morphogenetic gradients
Morphogen
A substance that creates a concentration gradient across a developing tissue, governing the tissue pattern and positions of specialized cells within tissues
Morphogenetic gradients generate_
different cell types in distinct spatial order, meaning certain area of tissue will have specific cells
Morphogens are the products of __ or __
genes, signaling molecule(retinoic acid)
What are some genes of bicoid?
Morphogens can be products of genes.
Homeobox gene: encodes for a transcription factor
Maternal effect gene: when it is mutant in the mother, the offspring will have a mutant phenotype regardless of their
own genotype
bicoid gene: sets up Anterior side larva, default is posterior
How does mRNA in bicoid relate to morphogens?
We known morphogens create a concentration gradient that leads to spatial cell specialization.
Bicoid:
mRNA is concentrated at A end of the mature egg, once fertilized it’s transcribed into protein. Then protein diffuses toward the posterior, resulting in a gradient aka morphogen. Bicoid bind to enhancer of genes involved in pattern formation, and turn on cells to form anterior structure.
What drives further differentiation of general categorizes in fruit flies?
Ex: posterior and anterior
Maternal mRNA is destroyed and the embryonic program of gene expression takes over to refine. Embryonic genes start encoding proteins and signaling molecules that are involved in gene activation/repression
