lecture 2 Flashcards
what are the main 4 developmental processes?
1) PATTERN FORMATION: embryo gets a polarity - anterior/posterior; dorso/ventral
2) MORPHOGENESIS: cells distribute themselves, changes in spatial distribution happen during gastrulation
3) CELL DIFFERENTIATION: cells change types leading to them having specific functions and specialized abilities
4) GROWTH:
- in size: when cells are duplicated and organism just becomes bigger
- morphogenetic: change in proportions of the organism as organs develop at different times and rates
what are the 2 kinds of proteins found within a cell?
1) HOUSEKEEPING PROTEINS: responsible for cell’s maintenance, survival, growth; ensure cells can undergo basic functions and the genes that encode for them are present in ALL cells (for example, receptors, intercellular cell-cell signaling proteins, growth factors)
2) TISSUE-SPECIFIC PROTEINS: are responsible for the cell to be able to execute its specific function or property (only expressed in certain cells); they can be edited at many different stages of synthesis
how can we demonstrate the STATE OF DETERMINATION of cells at any developmental stage?
By transplantation experiments
- if a cell is not determined, its fate is controlled by its surroundings: it can move from one region to another which will influence what it gets differentiated into
- if a cell is determined, its surroundings will not change what it becomes; it can move to different environments and will always end up being the same type of cell: its fate cannot be reversed or transformed
- if a cell is specified, it can be moved to a natural environment (ex: petri dish) and still become what it was meant to be.
what are the 2 types of embryo development?
1) Regulative embryos: flexible, very late differentiation (remove one of the cells, it simply becomes replaced)
2) Mosaic embryos: earlier determination, not so flexible (remove a cell = large consequences on final organism: parts of the body might not grow due to cytoplasmic localization of protein determinants and asymmetric cell division)
The key hypothesis of the mosaic model is that cytoplasmic determinants within the zygote are distributed unequally within daughter cells during cleavage stage. Each cell’s determinants control the future fate of the cell.
what is positional information?
each cell responds differently to a signal due to their location
ex: MORPHOGEN: a cell location will determine how it reacts to the morphogen as the concentration of the morphogen is not uniform
