Cell Reproduction

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  • Cell Reproduction
    • Clones
      • Natural
        • asexual reproduction produces genetically identical cells
          • plants have specialised parts that are derived from the adult plant cells, they can produce many new organisms that are genetically identical
            • known as Vegetative Propagation
        • Bacteria are prokaryotes, they have single, naked strands of DNA that is in their cytoplasm
          • they may also have plasmids of DNA that can contain genes for antibiotic resistance
            • because bacteria can swap plasmids, they are used in genetic engineering
          • Bacteria divide by binary fisson (mitosis can only apply when chromo-somes are used)
      • Artificial
        • cuttings taken from plants can be made to grow into genetically identical adult plants
        • In Animals : tissue biopsy is taken from donor animal
          • donor cells are grown in tissue culture
            • donor cell nucleus is transferred to recipient egg
              • cloned embryo is transferred to surrogate mother
                • pregnancy is monitored by ultrasound
      • genetically identical cells or organsisms derived from one parent
    • Stem Cells
      • cells that have the capability to divide and to develop into any of several different cell types
        • in young embryos stem cells can develop into any of the cell types found in the adult - they are TOTIPOTENT
        • In a small number of adult cells stem cells can be found - they are PLURI-POTENT - able to develop into several cell types
          • in bone marrow, stem cells can produce all types of blood and bone cell
        • stem cells have the capability to be widely used in medical treatments - using an individuals own cells to replace damaged/ diseased cells
    • Sexual Reproduction
      • fusing of two nuclei, usually from 2 different individuals, in order to produce off spring
      • each cell contributes half of the total genetic information (genome)
        • special cells containing half the number of chromo-somes must be produced - GAMETES
          • fusion of 2 gametes produces a Zygote, which can than divide by mitosis to grow into a new individual organism
    • Meiosis
      • takes place in specific regions of the adult organism - gonads
        • normal adult cells of most eukaryotes contain 2 sets of chromo-somes - DIPLOID
          • their genome consists of a pair of homologous chromo-somes, each containing the same genes, but not necessarily the same alleles of each gene
            • during meiosis, one member of each homologous pair goes into each daughter cell
              • the daughter cells are HAPLIOD and are not genetically identical
                • the haploid daughter cells differ because each pair of homologous chromo-somes separates  independently of each other. Each contains specific alleles of each gene on the members of the homologous chromo-somes they recieve
    • Division
      • in animals, many cells are capable of cytokinesis and mitosis - so organisms can  replace cells by producing new ones
      • in plants only the cells in special growing regions (meristems) known as meristem cells can divide that way
        • meristems are located at the root and shoot tips and in a ring of tissues in the stem or trunk. These small parts of the plant are responsible for the growth of the whole organism
      • Cytokinesis
        • in animal cells, starts from the outside, nipping in the cell membrane and cytoplasm along what is a 'cleavage furrow'
        • in plant cells, it starts with the formation of the cell plate where the spindle equator was. The cell lays down new membrane and cell wall material along the plate - CELL PLATE - not solid, but a  single plane which the new cell wall forms
        • Yeast cells under cytokinesis by producing a small bud that nips of the cell - BUDDING


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