an undifferentiated cell, that has the potential to differentiate into a range of specialised cells in an organism
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When do stem cells lose their ability to divide?
once stem cells become specialised,after differentiation-lose ability to divide cos they enter into G0 phase of cell cycle
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why is activity of stem cells strictly controlled?
if stem cells don't divide fast enough, then tissues wouldn't be replaced efficiently-leads to ageing 2)uncontrolled division can form masses of cells-tumours,which can lead to cancer
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Potency
A stem cell's ability to differentiate into different cell types
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what are the 3 types of potency?
Totipotent,Pluripotent & Multipotent
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Totipotent
stem cells that can differentiate into any type of cell & eventually produce whole organism e.g.8 or 16 cells from the first few mitotic divisions of a Zygote are totipotent
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Pluripotent
stem cells can form all tissue types but not whole organisms
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Multipotent
stem cells can only form a range of cells within a certain type of tissue e.g.Haematopoetic stem cells in bone marrow which differentiate into diff types of blood cells
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Erythropoiesis?
stem cells in bone marrow differetiate into erythrocytes(red blood cells).They lose their nuclei,mitochondria,RER & Golgi & change their shape into a biconcave disc
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why do red blood cells have a short life span of 120 days?
they lack organelles e.g.golgi,nucleus,RER
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2 Sources of Animal Stem cells?
1)Embryonic Stem Cells 2)Tissue(adult) Stem cells
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Embryonic Stem Cells
These cells are present at early stage of embryonic development & are totipotent.After 7 days, a mass of cells (blastocyst) has formed & now cells are pluripotent till birth
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Tissue (Adult) Stem Cells
They're multipotent,present from birth & throughout life.Found in specific areas in body e.g.Bone Marrow
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Name a great source of animal stem cells
Stem cells can be harvested from the umbilical cord-its great cos there's lots of umbilical cords,no need for invasive surgery,stored for future use & won't be rejected by the owner
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Source of plant stem cells?
stem cells are present in meristematic tissue/meristems-this tissue is found wherever growth is occuring e.g tips of roots & shoots or vascular cambium of xylem/phloem tissue
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what type of potency are the stems cells in meristem
they are pluripotent-this continues throughout the plant's life
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How are stem cells used to treat diseases?
they can be transplanted into specific areas of the body, that have been damaged, to replace those damaged cells
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Other cards in this set
Card 2
Front
When do stem cells lose their ability to divide?
Back
once stem cells become specialised,after differentiation-lose ability to divide cos they enter into G0 phase of cell cycle
Card 3
Front
why is activity of stem cells strictly controlled?
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