4 fundamental mechanisms that drive development
cell proliferation, cell specification (differentiation), cell rearrangements, cell signaling
3 ways to make organism larger
cell proliferation, cell enlargement, cell accretion
cell specification depends on…
regulation of gene expression
morphogenesis
the acquisition of embryonic shape
cell rearrangements depends on…
changes in the cytoskeleton
3 methods experimental embryologists used to study development of embryos
labeling, cutting, and transplantation
only organism with complete fate map
C. elegans
induction
ability of some embryonic cells to influence the fate of neighboring cells
how is induction accomplished
through cell signaling
epigenesis
acquisition of fate is progressive during development
what are the two mechanisms that controls the expression of the transcription factor at the beginning of the cascade
asymmetric distribution of cytoplasmic determinants and cell signaling
organizer
group of cells or region of embryo which produces signals which can influence/induce other cells to become specified
tight junction
seals neighboring cells together in an epithelial sheet to prevent leakage of molecules between them
adherens junction
joins an actin bundle in one cell to a similar bundle in a neighboring cell
desmosome
joins the intermediate filaments in one cell to those in a neighbor
gap junctions
form channels that allow small water soluble molecules to pass from cell to cell
hemidesmosome
anchors intermediate filaments in a cell to basal lamina
gene
DNA + promoter + regulatory sequences
gene expression
transcription + translation
expression pattern
spatial localization of genes within an embryo or organism where a gene is transcribed
morula
an embryo containing a few hundred cells that are morphologically equivalent to one another
RNA polymerase II
responsible for transcribing protein encoding genes; recognizes sequence at promoter and synthesizes mRNA sequence until it reaches a stop codon
what precedes the appearance of morphological structures
patterns of gene expression
general transcription factors
recognizes sequences in the gene promoter
enhancer
regulatory elements on DNA that control gene expression; can be located far away upstream or downstream from promoter; DNA sites to which activators bound
transcription factor
recognize enhancers; have homeodomain, Leucine zipper, or zinc finger
how transcription factors work
recruit mediators that facilitate or impede interaction between RNA polymerase II with general transcription factors; mediate changes in chromatin structure
methods of changing chromatin structure
changes in chromatin packing and changes in histone modification
master regulators
transcription factors that can initiate a complete development program by themselves; are necessary and sufficient to drive development; function by binding regulatory elements at different genes
example of master regulator
eyeless
methods of cell memory
positive regulatory feedback, regulatory cascades, epigenetic changes - DNA methylation and histone modification
epigenetic inheritance
transmission of epigenetic changes - DNA methylation and histone modification - through cell generations or organism to its descendants
