How does a multicellular organism develop from a zygote How is the position of the parts of an organism determined How does differentiation of cell type occur in organisms How are genetics and development connected Environment ID: 780170
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Slide1
Development
Slide2Big Questions:How does a multicellular organism develop from a zygote?How is the position of the parts of an organism determined?How does differentiation of cell type occur in organisms?How are genetics and development connected? Environment?
Slide3Development is Regulated The development of an organism is coordinated by sequential changes in gene expression. Multicellular organisms must regulate:Cell divisionDifferentiation
Morphogenesis
Slide4Early Developmental PathwaysCytoplasmic Determinants unequal distribution of mRNA and proteins from mother Embryonic Induction:Local signaling by nearby cells send cells down a specific developmental path.
Slide5Slide6Pattern Formation Cells need to establish their position in the developing organism. (head/tail, right /left etc.) Cytoplasmic determinants and induction lead to gradient morphogens.
Slide7Cellular Differentiation Germ lines establishedCell type already determinedDifferentiation accomplished by the expression of cell type-specific proteins. There is normally no turning back.
Slide8Differentiation ControlGenes must be both turned on and turned off at appropriate times and locations.Regulated by internal and external
cues
Slide9Internal Cues DNA packing, micro RNA’s and epigenetics can switch genes ON or OFF.Transcription factors must be present and can be either stimulatory or inhibitory.
Slide10External Cues (outside the cell)External cues signal to cells, causing cells to alter their gene expression.
Slide11Environmental Cues The presence of particular molecules and conditions in the local environment is required for development to proceed properly. Ex. The role of temperature and moisture in seed development.
Why do you water a seed after you plant it? Hmm…
Slide12Environmental CuesChanging the environment around the cells can alter gene expression.
Slide13Apoptosis “Programmed cell death”: Important role in defining borders and openings in the developingorganism.
Slide14Homeobox (HOX) GenesA family of related genes that serve as master regulators of animal development in all animals on the planet.
Slide15Experimental Evidence Mutations in normal developmental pathways lead to malformations in embryonic development
Slide16Experimental Evidence Transplantation Experiments: Moving regions of a developing embryo affects normal pattern formation.