cell division and stem cells

• A always pairs with T
• C always pairs with G
• chromosome are found in the nucleus of every cell
• chromosomes are only visible when a cell is about to divide
• the chromosome is made of the chemical DNA
• sections of DNA that control features of the organism are called genes
• human body cells have 46 chromosomes
• the purpose of mitosis is growth and repair
• 2 daughter cells are produced by mitosis
• daughter cells in mitosis are genetically identical
• daughter cells in mitosis have the same number of chromosomes as parent cells
• meiosis produces 4 daughter cells
• the daughter cells produced by meiosis are genetically different
• in meiosis daughter cells have half as many chromosomes as the parent cell
• the purpose of meiosis is the formation of gametes and sexual reproduction
• diploid - the same number of chromosomes as the parent
• haploid - half the number of chromosomes as the parent
• differentiate - to become specialised in some way
• Once a stem cell has differentiated, if they can divide, they can only form similar cells to themselves
• scientists can take stem cells from an embryo and grow them into types of cells that can be used to repair or replace damaged tissue
• positives of using stem cells -

  • used to treat diseases (e.g. cancer, type 1 diabetes)
  • used to repair damaged tissue (e.g. brain damage, spinal cord injuries)
• negatives of using stem cells -

  • any embryo has the potential to develop into a human being, and so the process destroys life.
  • some people are worried that embryos might be created specifically to produce stem cells, so it would be rather like 'farming' human beings
• stem cells can be found in adults (e.g. bone marrows in bones)
• stem cells from adults are unable to develop into as many different types of cells as embryonic stem cells
• stem cells can also be collected from the blood from the umbilical cord at birth
• stem cells in plants are found in the growing areas (meristems) in roots and shoots
• stem cells in plants can be used to cultivate new plants but have no medical uses