Cell division

• Stage 1: interphase


  Each chromosome is copied

  making more organelles

  replication of DNA to form two copies of each chromosomes and synthesis of sub-cellular structure
• Stage 6: cytokinesis


  cytoplasm divides

  cell membrane divides

  cell divides
• Binary fission


  bacteria divides

  plasmids replicates

  pulled to opposites sides

  squished together until it splits
• adult stem cells


  can only differentiate to form certain types of cells
• mitosis 


  growth of organisms

  repair tissues

  asexual reproduction

  46 chromosomes - replicates - 2 genetically identical daughter cells - diploid
• meiosis


  makes gametes/ sex cells

  46 chromosomes- replicates - divides into 2- then divide those 2 into 2 more - produces 4 genetically unique cells - haploid
• At the end of a root tip and shoot tip in an area called meristems. undifferentiated plant cells are found in meristems
• Ethics of using stem cells

  • embryo cannot give permission
  • embryo is destroyed
  • differentiation signals not fully understood
  • may cause cancer
  • may be infected with virus
  • person may need to take immunosuppressant drugs
  • expensive
• stage 2: mitosis


  replacement of damaged cells

  the chromosomes are pulled to each end of the dividing cell and then the nucleus divides
• differentiate


  the process where cells become specialised for a particular function.
• where are adult stem cells found?


  specific parts of the body in adult and children
• Advantages of adult stem cells

  • fewer ethical issues - adult consent for their stem cell to be removed
  • established technique for treating diseases
  • relatively safe to use as a treatment
• Disadvantages of adult stem cells

  • requires a donor
  • can only differentiate into certain types of specialised cells - treats fewer diseases.
• where is an embryonic stem cell found?


  in early human embryos
• what can embryonic stems cells differentiate into?

  can differentiate into any type of specialised cell in the body.
• advantages of embryonic stems cells

  • can treat a wide range of diseases
  • may be possible to grow whole replacement organs
  • usually no donor needed.
• Disadvantages of embryonic stem cells

  • ethical issues - each embryo is a potential human life.
  • risk of transferring viral infections to the patient
  • newer treatment so relatively under researched
• Plant meristems location?


  meristem regions in the roots and shoots of plants
• what can plant meristem differentiate into?

  can differentiate into all cell types
• advantages of meristems

  • rare species of plants can be cloned
  • plants with desirable traits can be cloned
  • fast and low-cost production of large numbers of plants
• disadvantages of meristems

  • cloned plants are genetically identical, so a whole crop is at risk of being destroyed by a single disease.