LS19Transgenicmodels

LS19Transgenicmodels - Lecture 19: Gene manipulation in an...

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1 Lecture 19: Gene manipulation in an organism 2. Transgenic plants 3. Transgenic animals 4. Using transgenic techniques to study gene function: knock-out and knock-down mutations 5. Gene Therapy 6. Animal cloning 1. Transgenic organisms Transgenic organisms are organisms transformed to contain the recombinant foreign DNA. This technology is the foundation for many molecular biology researches. Unlike single cell organisms, multicellular organisms are difficult to transform. Transgenic organisms usually refer to multicellular organisms such as transgenic plants or transgenic animals. Two problems in preparing transgenic organisms: (1) recombinant DNA must be delivered into a host cell and be integrated into the host genome; (2) The transgenic cell must be able to develop into the whole organism
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2 Stem cell: embryonic stem cells differentiate (become different) into different types of cells. The differentiation of animal cells is irreversible. But some cells can keep relatively undifferentiated status, they are called stem cells or progenitor cells fertilized egg (totipotent ) stem cell (pluripotent ) Male and female pronuclei Fates of a cell (also read text page 899-902) Totipotency - Totipotency is the ability of a cell to give rise to a whole new organism. Pluripotency is the ability to give rise to all types of cells but not the whole organism. - Stem cell is the cell that can reproduce itself and differentiate into other types of cells. Embryonic stem (ES) cells are cells isolated from the inner cell mass of blastocyst (early embryos). ES cells can differentiate into all types of cells (but not the whole organism), so they are pluripotent. Somatic stem cells can produce limited types of cells, so they are called multipotent . - Plant cells are generally totipotent, so a transgenic plant can be obtained from regeneration of a single plant somatic cell - Animal cells are not (yet) totipotent. The only known totipotent animal cell is the fertilized egg
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3 2. Plant transformation and cloning Plant Transformation: A soil bacterium called Agrobacterium tumefaciens harbors a plasmid known as T i plasmid. T i plasmids can deliver their DNA into the plant genome and it is used as the vector in plant transformation. When plant cells or tissues are infected with Agrobacteria containing recombinant T i plasmid, T i plasmids will migrate from bacterial cells into plant cells, and integrate its T-DNA into the plant genome, resulting in transgenic plant. Plant Cloning: Because plant cell is totipotent, plant cloning is relatively easy, a single cell transformed with recombinant DNA can be regenerated into a new plant, which can self-fertilize to produce clones T L T R T-DNAs are the sequences essential for integration of the DNA between them into plant genome Plant promoter X X gene to be transformed ori Transgenic plants are resistant to Basta herbicide and they express the gene X X The region between two T DNAs is
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LS19Transgenicmodels - Lecture 19: Gene manipulation in an...

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