B2.1 cell division

  • In bodies cells, chromosomes are found in pairs. 
  • Body cells are divide in a series of stages called yhe cell cycle.
  • During the cell cycle the genitic material is doubled. it then divides into two identicle nuclei in a proccess called mitosis.
  • Before a cell can divide it needs to grow, replicate the DNA to form two copies of each chromosome and increase the number of subcellular structures. In mitosis one set of chromosomes is pulled to each of the cell and the nucleus divides. Finally the cytoplasm and cell membranes divide to form two identical cells.
  • mitotic cell division is important in the growth, repair and development of multicellular organisms. 
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B2.1 growth and differentiation

  • In plant cells,mitosis takes place throughout life in the meristems found in the shoot and the root. 
  • Many types of plant cells the ability to to differentiate throughout life.
  • Most types of animal cells differentiate at an early stage of development and cell division is mainly for repair and replacment 
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B2.3 stem cells

  • Embryonic stem cells (from human embryos) and adult stem cells (from adult bone meal can be cloned and made to differentiate into many different types of cell. 
  • Treatment stem cells may be able to help conditionssuch as paralysis and diabetes.
  • Stem cells from plant meristems are used to produce new plant clones quickly and economiclly for research , horticulture, and agriculture. 
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B.3 stem cell dilemmans

  • Treatment with stem cells, from embryos or adult cell cloning may be able to help with conditions sutch as diabbetes. 
  • In therapeutic cloning an embryo is produced with the same genes as the patient,so the stem cells produced are not rejected and may be used for medical treatment.
  • The use of stem cells has some potencial risks and some people have ethical or religious objections. 
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