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Published byDaniel Lucas Modified over 8 years ago
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Aim #55: How does an embryo develop?
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How does the zygote form? Zygote – A fertilized egg
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What happens to the zygote after it is formed? Mitosis – causes the zygote to repeatedly divide producing the developing embryo.
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Embryonic Development: + SpermEgg Fertilization Zygote Mitosis Embryo- the stage in human development from the first division of the zygote until about nine weeks after fertilization.
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Cleavage The term used to describe the early cell division associated with embryonic development. During this time period, the number of cells increase tremendously.
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The result of cleavage is an embryo that is ….. A solid ball of cells which moves towards the uterus Morula
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Mitosis continues & the embryo becomes…… A hollow ball of cells Blastocyst
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Cell division continues & the embryo starts to …. Gastrula Fold inwardly
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Gastrulation Three layers Each layer will eventually form the different organ systems
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CELLULAR DIFFERENTIATION Due to gene expression, cells undergo cellular differentiation, in which the cells become increasingly specialized in structure & function.
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Gene Expression Though all genes of the genome are present in every type of cell, only a small, specific fraction of these genes are actually expressed in each type of cell. Genes that are being expressed are “on”
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What makes some cells turn “on” some genes while other genes are “off”? Environmental influences from within the cell, from surrounding cells, or from outside the organism.
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Why are they different? These seeds carry the same genes for chlorophyll: CC Grown in light Grown in dark ENVIRONMENT AFFECTS GENE EXPRESSION
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Differentiation’s ultimate goal An embryo with many different types of cells
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Stem Cells Stem cells are embryonic cells that can turn into any type of cell in the body
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How can stem cells help us? Can be used to make any type of cell that needs to be replaced in our bodies
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Why is the use of stem cells so controversial? They are often taken from fetuses. Opponents believe that you are killing a life.
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Are stem cells only embryonic? No, there are some adult stem cells, but they don’t have the potential to become any kind of cell
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A Cell Stem Story Award-winning 15 minute video introduction to stem cell research http://www.eurostemcell.org/films
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