B2 - Cell division Flashcards
Describe the 3 stages of the cell cycle:
-cell increases number of ribosomes and mitochondria and chromosomes replicate
-(mitosis) one set of chromosomes is pulled to each end of the cell, nucleus divides
-cytoplasm + cell membrane divides to form two daughter cells with identical sets of chromosomes
What is mitosis important for?
the replacement/growth/repair of multicellular organisms
What is a stem cell and what can it do?
undifferentiated cell of an organism which can divide by mitosis to self-replicate, and can also differentiate to form specialised cells
What is differentiation?
the process of stem cells becoming specialised
Where do you get stem cells from in animals/plants and why are they different to plants?
-embryo (embryonic at birth)
-bone marrow (adult SC)
-meristems
-can only differentiate once in animals
How is a stem cell different to a body cell?
-yet to go through differentiation
-doesn’t have specialised structure/shape to perform specific tasks
What does therapeutic cloning do?
-produces an embryonic stem cell with the same genes as the patient
-can be used without the risk of rejection
Describe the process of therapeutic cloning:
-remove nucleus of unfertilised donor egg cell and replace it for the nucleus from an adult body cell (eg skin cell)
-give egg cell electric shock so it starts to divide by mitosis
-separate off to form different specialised tissues under specific conditions
Give some pros of using embryonic stem cells:
-can differentiate into any type of cell
-less waiting for organ transplant
-offers treatment to many diseases (paralysis/T1 diabetes)
Give some cons of embryonic stem cells:
-ethical issues surrounding using embryos (eg consent, creating embryos for research only)
-need immunosuppressants
-viral infection possible
Name the pros of adult stem cells:
-consent from donor
-can be self donated (no chance of rejection/viral infection if you aren’t already infected)
Give some cons of using adult stem cells:
-far less potential for differentiation
-viral infection possible
-painful transplant
Why would you want to clone plants?
-rare species can be protected from extinction
-clone crops with desirable adaptations (eg pathogen resistance)
Why might the growth of cells in a culture medium level off?
-shortage of nutrients/oxygen
-cell death rate = cell division rate
Don’t say cell growth rate as cells growing doesn’t contribute to a population increase
