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Structure, function and growth of prokaryote and eukaryote cells (iii) Differentiation of cells into tissues and organs. (iv) Cell and tissue culture – Mammalian cell cultures – Bacterial and Fungal Cultures (v) Plant tissue culture
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Development An organism starts life as a zygote (single fertilised cell). It undergoes three main stages to develop into an individual 1. Mitotic division to form a group of cells called the blastula. 2. Gastrulation Infolding of the cells to form a cup shape called a gastrula
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Development cont… – The gastrula has three germ layers Endoderm – Develops into the alimentary canal Ectoderm – Develops into skin and nervous system Mesoderm – Develops into the muscles, skeleton, circulatory system, excretory system
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Development cont… 3. Cell division and differentiation (specialisation) results in tissue and organ formation.
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Differentiation Nearly all cells in an organism have the same DNA Differentiation depends on gene expression (the transcription of a gene into mRNA) i.e. which genes are ‘switched on’ and which genes are ‘switched off’.
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Differentiation cont… During development the control of gene expression may be: Temporal (different genes expressed at different times in development) Spatial (cells in different places in the embryo expressing different genes) Example of differentiation to form an organism: Drosophila melanogaster
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Control of Gene Expression in Bacteria Lac operon (aka Jacob-Monod hypothesis)
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Stem Cells A stem cell is an undifferentiated cell which can undergo unlimited division to form other cells Source of stem cells – Adult e.g. bone marrow – Embryonic (from blastula stage ~ 150 cell stage) – Cancer cells – Umbilical Cord Blood Stem cells have the ability to differentiate, unlike specialised cells
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Learning Activities Differentiation of Human Cells Read DART pg 18-20 Scholar (Unit 1, no. 2) Web animations from Biozone website http://www.sumanasinc.com/webcontent/anisamples/nonmajor sbiology/stemcells.html http://www.sumanasinc.com/webcontent/anisamples/nonmajor sbiology/stemcells.html http://www.sumanasinc.com/webcontent/anisamples/majorsbio logy/lacoperon.html http://science.howstuffworks.com/stem-cell.htm
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