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Chapter 19 Notes Nematode Caenorhabditis elegans develops __________________ from a single fertilized egg All _____________________ develop according to molecular mechanisms that are fundamentally very similar • This suggests that these mechanisms evolved very early on • 6 Mechanisms – _______________________ – _______________________ – _______________________ – _______________________ – _______________________ – _______________________ Cell Movement Cells can move by _______________ along with adhesion molecules. • Some tissues have most of volume taken up by intercellular spaces filled with matrix of polysaccharide chains. • Migrating cells traverse by binding _______________________________. • The movement of cells involves _______________ and loss of __________ • Involves _____________ interactions and ________________ interactions • Cell migration is largely a matter of changing ____________________ Induction Induction: __________________________________________________________ ___________________________ Mosaic development vs. regulative development – mosaic – _______________________________________________ ______________________ – Regulative – _______________________________________________ ___________________________ • Cell-cell interactions can be demonstrated by separating the cells of an early blastula and allowing them to _____________________________ • Under these conditions __________________ cells develop features of ectoderm and ________________________ cells develop endoderm – Mesoderm features are not seen • If the cells from opposing poles are placed near each other, then ____________ features are seen • The interaction of two cell types triggers a ____________________________ • Induction - Figure 19.10 Development of the vertebrate eye by induction. – The eye develops as an _________________________ called the optic stalk that grows out until it contacts the ectoderm. This contact induces the formation of a lens from the _____________________ Organizers: groups of cells that produce ___________________________ that convey ______________________ to other cells • They have a profound influence on the ________________________ • Morphogen: signal molecule have different effects ___________________ Determination • Mammalian cells are ____________ - potentially capable of _______________ ___________________. • The vertebrate egg is _________________________ as well as its shape. All cells of the _____________ are the same • If separated, any cell can produce a ____________________. • This has been used to create 8 identical offspring (cattle) – If cells from two different eight-cell embryos are combined, a normal individual results ________________. – Mammalian cells begin to differentiate after the ______________________. – ______________ is the commitment to a specialized developmental path. – ______________ is the cell specialization that occurs at the end of the developmental path. – Determination is _________________. – Given proper technique, fate of fully differentiated cell can be altered. – Gene regulatory proteins initiate ____________________ – When genes encoding these proteins are activated, one of their effects is to reinforce their own activation – Cells in which a set of regulatory genes have been activated may not undergo differentiation, but once the “switch” is thrown, the cell us fully committed to its future development. This experiment, the first successful cloning of a mammal shows that a differentiated adult cell can be used to drive all of development Animals use _________ _________________ to determine the basic pattern of body compartments and overall architecture of the body. Body organization in the developing Drosophila embryo • Drosophila egg acquires initial asymmetry as a result of maternal mRNA. • Fertilization causes mRNA to be translated into bicoid protein. establishes anterior end of embryo if injected into posterior end of normal embryos, head and thorax will develop at that end • Within three hours after fertilization, orchestrated ________________ gene activity produces fly ____________________. – Gene activation depends on free diffusion of _______________ through ______________________. • After pattern formation has been established in Drosophila, a series of homeotic genes determine the forms these segments will take. – code for proteins that function as __________________ • Mutations in homeotic genes can cause normal body parts in unusual places. – typically contain the __________________ • also been found in mice and humans Homeobox • A 180 nucleotide sequence that codes for a 60 amino-acid DNA-binding peptide called the ________________ • Contain ______________________ which ensure that developmentally related genes are transcribed at the appropriate time • Bicoid and engrailed genes in the homeobox Apoptosis • Not all cells produced are destined to survive • Cells between ________________________ die • _______________ – cells that die due to injury typically swell and burst, releasing their contents into the extracellular fluid • _______________ – programmed cell death • All animal cells appear to posses “death program” • Examples?