cell division

• The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of genes. In body cells the chromosomes are normally found in pairs.
• mitosis: a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth
• steps of mitosis

  1. genetic material is doubled
  2. cells grow and increase the number of sub-cellular structures such as ribosomes and mitochondria
  3. DNA replicates to form two copies of each chromosome
  4. one set of chromosomes is pulled to each end of the cell and the nucleus divides
  5. cytoplasm and cell membrane divide to form identical cells
• A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
• Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
• Stem cells from adult bone marrow can form many types of cells including blood cells.
• Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
• Treatment with stem cells may be able to help conditions such as diabetes and paralysis.
• In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.
• for therapeutic cloning:

  • can be used to treat many diseases including diabetes and nerve paralysis. therefore more lives are saved in the long run
  • can be used for research to help discovery of treatments
• against therapeutic cloning :

  • destruction of embryos produces from fertilisation. some people believe that life starts after fertilisation so it is killing. religious/moral issues
  • if the sample of stem cells is contaminated by a virus they could be transmitted to the patient. could have negative implications
• Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.

  • Rare species can be cloned to protect from extinction.

  • Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.