Topic 3: Stem cells Flashcards
Describe how the body uses stem cells
4 points
- They are the foundation for every body organ and tissue.
- When a stem cell divides, each new stem cell either REMAINS A STEM CELL or can become SPECIALISED into a certain cell type.
- In many body tissues, stem cells divide regularly eg. in gut and skin, stem cells can give rise to new cells to repair and replace {worn out/damaged} tissues.
- In other organs eg. pancreas and the heart, stem cells divide more rarely
Define stem cell (3 points)
- An {UNDIFFERENTIATED/unspecialised} cell that can GIVE RISE TO other TYPES OF SPECIALISED CELL,
- are capable of self-renewal with no limit to division
- and can be totipotent, pluripotent or multipotent.
Define totipotent stem cells (2 points)
- {undifferentiated/unspecialised} cells which are capable of self-renewal, with no limit to division,
- that can GIVE RISE TO ALL CELL TYPES including extra embryonic cells
Note: Totipotency is therefore a ‘property’ of the very earliest {embryonic/totipotent} stem cells. They have ‘total potential’.
What is a source of totipotent stem cells? (2 sources)
- Zygote to
- 8 cell embryo
NOTE: Also anywhere between the zygote and 8 cell embryo
Define pluripotent stem cells (2 points)
- {undifferentiated / unspecialised cells}, which have SOME genes switched off,
- which can give rise to MOST TYPES of specialised cells, but NOT totipotent embryonic stem cells
What is a source of pluripotent stem cells? (2 sources)
- from INNER CELL MASS OF A BLASTOCYST
2. from UMBILICAL CORD BLOOD
Define multipotent stem cells (2 points)
- {undifferentiated / unspecialised} cells, which have MANY genes switched off,
- which can give rise to a SMALL number of different, closely related specialised cell types
NOTE: Often called “adult stem cells” - but are found in the body from birth onwards - found among the differentiated cells in many parts of body
Where from the body can multipotent stem cells be collected? (1 source)
- bone marrow
NOTE: can also be obtained from the brain (more difficult to obtain)
Key Summary: What are the important properties of stem cells?
(3 properties)
- Have the potential to give rise to specialised cells
- Can continue to divide with no limit to division
- Totipotency or pluripotency or multipotency
Key Summary: For 7 sources, give: the source, type of cell, and potency of those stem cells.
NOTE: type of cell is either {embryonic/non-embryonic/adult} stem cells
- Zygote - embryonic stem cells - totipotent
- 8 cell embryo - embryonic stem cells - totipotent
- blastocyst inner cell mass - embryonic stem cells - pluripotent
- umbilical cord blood - non embryonic stem cells - pluripotent
- placenta - non embryonic stem cells - pluripotent
- bone marrow - adult stem cells - multipotent
- {brain/connective/skin/liver} cells - adult stem cells - multipotent
NOTE: {multipotent/adult stem cells} can be extracted from birth onwards
(plant stems and tissue culture)
________ _________ in the {medium/agar} help unspecialised stem cells ____________ into specialised cells.
Growth regulators
differentiate
(Plant stem cells and tissue culture)
Describe the method to find out which plant tissues are totipotent (contain totipotent stem cells)
(8 steps)
- Take 5 {samples / explants} from a plant tissue(s)
- Use aseptic {technique/conditions} eg. sterile agar, scalpel
- Place 5 explants into bottles of agar which contains growth regulators, glucose, minerals
- Place under a light bank for 14 days to control light intensity with heat shield between light and explants to absorb heat and control temperature
- Grow cells into a callus
- {{Cells / tissue} differentiate / cells become whole plants}
- Record results (eg. new leaves) every day for 14 days
- Other controlled variables - same {volume of agar / concentration of growth regulator}
(Plant stem cells and tissue culture)
What is the purpose of aseptic technique? (1 point)
- Prevents pathogenic {microbes/bacteria/fungi} from {contaminating/entering} bottle
(Plant stem cells and tissue culture)
What is the purpose of a heat shield? (3 points)
- Controls temperature,
- prevents explants drying out
- and prevents plant enzymes being denatured
(Plant stem cells and tissue culture)
What is the purpose of a light bank? (2 points)
- Controls light intensity
2. provides light for photosynthesis
(Plant stem cells and tissue culture)
What is the purpose of having glucose and minerals in agar? (1 point)
- For plant growth and development (glucose for respiration to release ATP, magnesium for chlorophyll, nitrates to make proteins for growth)
(Plant stem cells and tissue culture)
What is the purpose of growth regulators? (1 point)
- To allow totipotent stem cells to differentiate into different cell types
(Plant stem cells and tissue culture)
What is the purpose of covering the bottles in cling film? (3 points)
- For safety - prevents pathogenic {microbes/bacteria/fungi} from {contaminating/entering} bottle
- Allows light in for photosynthesis
- and reduces water loss
(Plant stem cells and tissue culture)
For the experiment of which plant tissues are totipotent, how will you know whether the tissue contains totipotent stem cells? (1 point)
- If the stem cells in the plant tissue are totipotent, then eventually a whole new plant (roots, stem, leaves – all cell types) will be produced.
NOTE: You will find out that ALL plant cells are totipotent – they are capable of developing into any of the cell types needed to make a new plant, so every explant should form a new plant
Describe the steps for plant tissue culture in plant breeding
(5 steps)
- Explant taken from parent plant
- Placed on nutrient agar with growth regulators
- Cells divide to form a callus, then embryo
- Embryo grows into tiny plant
- Tiny plant can be planted in compost and grown on
What are the applications of plant tissue culture?
5 points
- Developing improved {plant/food crop} species
- to INCREASE THE DISEASE RESISTANCE of plants
- to produce commercial plants that are DIFFICULT TO GROW FROM SEED (eg. orchids)
- Produce increased quantities of PHYTOCHEMICALS USED IN DRUGS (eg. the anti-cancer drug Taxol from Yew trees)
- CONSERVATION of endangered plant species
Commercial benefits of plant tissue culture
2 benefits
- Can guarantee the QUALITY of the the identical plant produced
- Often EASIER AND QUICKER THAN GROWING PLANTS FROM SEED
Research benefits of plant tissue culture (1 benefit)
- CAN EXPOSE CLONED PLANTS TO DIFFERENT EXPERIMENTAL CONDITIONS and differences in behaviour or development can then be reliably put down to an experimental variable, as all plants are genetically identical.
Key Summary: Give the uses of stem cells in medicine
2 uses
- Producing ORGANS FOR TRANSPLANT
2. Producing NEW TISSUES FOR REPAIRING OR REPLACING DAMAGED TISSUES eg. in heart or spinal cord