B2. Cell division and Stem Cells Flashcards
Why do cells divide by mitosis?
- To allow growth
- To repair body tissues
- To replace old/dead/worn out cells
What are the 3 stages of the cell cycle?
- Interphase
- Mitosis
- Cytokinesis
What happens during interphase?
- The cell grows in size.
- DNA replicates
- Organelles replicate.
What happens during mitosis?
- The replicated chromosomes line up along the centre of the cell.
- Spindle fibres contract and the chromosomes get pulled to opposite poles.
- Nucleus divides.
What happens during cytokinesis?
- Cell membrane and cytoplasm divide.
- 2 genetically identical daughter cells are formed.
What are the products of mitosis?
2 genetically identical daughter cells
What is a stem cell?
A cell that has not yet become specialised cell.
Give 2 properties of a stem cell?
- Can replicate many times
* Has the potential to become specialised (i.e. different types of cell).
What are the 2 main types of stem cell?
- Embryonic stem cells (from embryos)
* Adult stem cells (from adult tissues)
Where are embryonic stem cells found?
Embryonic stem cells are stem cells found in embryos.
Where are adult stem cells found?
Adult stem cells are stem cells found in adult tissues (such as bone marrow, brain, muscle, liver stem cells).
Where are stem cells found in plants?
- They are found in the meristems of a plant.
* Found in root and shoot tips
What are the advantages of using embryonic stem cells to treat diseases?
- Have the potential to develop into any type of cell/tissue.
- Cells can become any cell type.
- Used to treat human diseases.
- Painless
What are the advantages of using adult stem cells to treat diseases?
- Plentiful supply
- No ethical issues (in collection) as the person can give consent.
- Safer method as it is well tried/tested.
What are the disadvantages of using embryonic stem cells to treat diseases?
- Unethical – embryos cannot give permission.
- Possible harm/death to embryo.
What are the disadvantages of using adult stem cells to treat diseases?
- Painful to extract
- Fewer diseases can be treated
- Can only form the type of cells as the tissue they were taken from.
- Possibility of infection during extraction of stem cells.
Name a disease that stem cells have been used to treat.
- Paralysis
- Diabetes
- Eyesight in the blind
What is therapeutic cloning?
Therapeutic cloning involves an embryo being produced with the SAME GENES as the patient.
Describe the stages of therapeutic cloning.
- The nucleus from a human skin cell (donor) is removed & kept.
- Nucleus from a human egg cell is removed and discarded.
- Skin cell nucleus is inserted into the empty egg cell.
- Egg cell is given an electric shock to stimulate it inot dividing.
- This develops into an embryo.
- The cells from this embryo are stem cells & are used to treat diseases.
How do you answer an ‘evaluate’ type question in the exam?
In the exam they often ask questions where they ask you to ‘evaluate’ stem cells or stem cell treatments. If you see the word evaluate your answer needs to include:
• Comparison 1
• Comparison 2
• Comparison 3 (use the data if provided)
• Use the word WHEREAS to link 2 comparisons e.g. Ms Lee is a Biology teacher WHEREAS Mr Araim is a Physics teacher.
• A balanced conclusion using data if it is given. i.e. must state _________ is ‘better because….’
What is meant by the term ‘differentiation’?
Differentiation is the process by which a cell changes to become specialised for it’s job.
What is a ‘specialised cell’
A specialised cell is a cell that has a specific structure and performs a specific function.
When do animal cells lose the ability to differentiate?
Animal cells lose the ability to differentiate after they become specialised.
What type of cells can adult stem cells differentiate into?
They can only differentiate into cells from the type of tissue where they are found. e.g. liver stem cells can only become liver cells.
What type of cells can embryonic stem cells differentiate into?
Embryonic stem cell can differentiate into almost every cell type under the right conditions in a lab.
When do plant stem cells lose the ability to differentiate?
Stem cells (found in meristems) can differentiate into any type of plant cell throughout the plants entire life.
