Cell division

• Gene


  section of DNA that controls a characteristic, or part of a characteristic of your body
• Cell cycle stage 1

  cell grows bigger, replicates DNA to form two copies of each chromosome ready for division. increases number of subcellular structure, such as ribosomes, chloroplasts and mitochondria
• Cell cycle stage 2 


  One set of chromosomes is pulled to each end of the dividing cell and the nucleus divides
• Cell cycle stage 3

  Cytoplasm and cell membrane divides to form 2 identical daughter cells
• What is a chromosome


  coiled up lengths of DNA molecules carrying a large number of genes
• What is DNA


  unique chemical that makes up genetic material
• Why is cell division by mitosis so important in the body?

  -growth and development.

  -replacement of damaged cells

  -produces cells with same chromosomes and identical genetic material which fulfil same functions as original cell
• Why is it important for chromosome number to stay the same when the cells divide to make other normal body cells?

  -may lack vital genes

  -new cells would not work properly

  -organism might die
• What differentiated cells cannot divide at all?

  -red blood cells and skin cells, therefore adult stem cells replace dead or damaged cells
• Why are nerve cells not replaced when they are damages?

  -they do not divide and are not replaced by stem cells
• What is the difference in differentiation between animal cells and plant cells?

  -plant cells can differentiate all through their lives, whilst animal cells only differentiate during embryo development

  -plant cell differentiation is not permanent and they can re-differentiate, whereas in animal cells it is permanent and they cannot re-differentiate
• What is cell differentiated

  When a cell becomes specialised and adapted to perform a particular function
• Why is differentiation important in living organisms?

  -all cells in an early animal or plant embryo are unspecialised

  -differentiation fulfils organism's requirements for different cells to carry out different roles
• Discuss how the difference in differentiation patterns affects our ability to clone plants and animals

  -in plants differentiation can be reversed and mitosis induced

  -conditions can be changed to induce more mitosis

  -cells redifferentiate into different plant tissues to form a new clone plant

  -so plants can be cloned relatively easily

  -in animals differentiation cannot be reversed

  -so clones cannot be made easily

  -in order to make animal clones, embryos have to be cloned
• what is a zygote


  a fertilised egg cell
• Differences between a stem cell and a normal body cell


  Stem cell :

  -undifferentiated cell

  -with potential to divide by mitosis, differentiate and form different specialised cells in the body

  Normal body cell:

  -specialised for specific function

  -division by mitosis can only form cells with the same specialisation
• Three sources of stem cells

  -embryos

  -bone marrow

  -plant meristem
• Advantages of using stem cells to treat diseases:

  -embryonic stem cells can make any type of adult cell to repair or replace damaged tissues

  -could grow organs for transplants as needed

  -organs grown from stem cells could cause fewer rejection issues if right techniques used
• Why is cloning large numbers of individual plants an advantage in plant research?

  -In research it is important as far as possible to change only one variable.

  -Ability to produce large numbers of identical plant clones enables researchers to change a variety of different variables and see effects on genetically identical individuals

  -Any differences will be due to variables under investigation, not genetic differences between plants
• Suggest how cloning plants may enable us to save rare species of plants from extinction

  Single rare plant specimen may not reproduce or researchers may not understand conditions needed for it to thrive.

  If specimen dies or does not make seeds, species will be lost.

  Cloning allows scientists time to find out about the plant and to find other specimens to introduce long‑term genetic variation.
• Advantages of cloning plants

  -horticulture: cloning allows production of large numbers of genetically identical plants with known desirable characteristics more economically and quickly than by normal plant reproduction

  -rare plants: cloned to conserve them and prevent extinction cannot be guaranteed by normal plant reproduction research: production of large numbers of genetically identical plants for

  -research more economical and quicker than by normal plant reproduction effects of different variables can be seen more quickly
• What is therapeutic cloning?


  -using cells from an adult to produce cloned early embryo of themselves

  -same genetic material as patient so would not be rejected
• Three areas of medical research where use of stem cells could provide valuable medical treatments

  -spinal chord damage

  -diabetes

  -heart after damager in a heart attack

  -eyesight in the blind

  -damaged bone and cartilage
• Main arguments for and against use of embryonic stem cells in medical research

  For:

  -potential to cure many currently untreatable diseases/injuries

  -grow new organs for transplant

  -prevent organ rejection

  Against:

  -problematic for some

  -risk of side effects (cancer, viral infection)

  -development of treatment slow and expensive

  -difficult to control stem cells

  -patients may need immunosuppressant drugs

  -is relatively new research, still discovering
• How are scientists hoping to overcome ethical objections to using embryonic stem cells in their research?

  -using embryonic stem cells from umbilical chord blood/amniotic fluid

  -using adult stem cells where possible

  -therapeutic cloning, cells originate from patient so no reproductive embryo and no immune problems
• How would you expect cell cycle to differ between a 13 year old student and 70 year old adult

  13 year old:

  -cell cycle rapid

  -growth and development take place during puberty, requiring new cells

  70 year old:

  -cell cycle slow, new cells still needed for repair, but not for growth

  -cell death beginning to overtake cell division
• Why is the cell cycle important during the development of a baby from a fertilised egg and all throughout life?

  mitosis responsible for all cell divisions

  from fertilised egg to development of baby

  after birth, mitosis responsible for all cell divisions for growth repair replacement of damaged tissues

  requirement for cell replacement and repair continues throughout life
• How may many different medical problems be cured with stem cells


  stem cells may be used to create almost any different type of body cell new cells grown from stem cells may be used to repair damaged body parts

  grow new organs for transplant restore eyesight
• When would the cell cycle be the shortest?


  In an embryonic stem cell because they are forming new tissues and are growing/dividing the fastest
• Where in the adult body are stem cells common?


  -bone marrow

  -hair follicles

  -skin

  -blood

  -lining of digestive system
• pros and cons of therapeutic cloning

  pros:

  • many cells could be produced
  • cells / tissues of any type could be produced
  • stem cells would not be rejected by the patient
  • stem cells would be produced that could be used for research
  • sexual reproduction / fertilisation not involved
  • would reduce waiting time for organ transplants
  • cons:
  • shortage of donor eggs
  • egg donation / collection painful
  • poor success rate to produce viable eggs
  • embryo is destroyed
  • could lead to cloning of humans in the future
  • justified conclusion
• How does therapeutic cloning work

  -egg cell donated

  -nucleus in egg cell removed and nucleus from patient's cell transferred

  -cell is simulated to divide

  -cell develops into an embryo

  -stem cells removed from embryo and cultured into therapeutic cloning