Stem Cells

• Found in most multi-cellular organisms, it is essentially the building block of the human body and the earliest human stem cell is found in the embryo, a stem cell is a single cell that can replicate itself or differentiate into many cell types
• The difference between a heart cell and a liver cell is that they carry a different set of genes each, likewise, a stem cell turns on specific sets of genes to differentiate into another cell
• Embryonic Stem cells: Present in an early embryo, form when the zygote (fertilised egg) starts to divide, they differentiate into all of the specialised embryonic tissues (e.g. placenta or umbilical cord), so produce a completely viable organism
• Embryonic Stem cells: After IVF many couples donate their unused embryos for stem cell research, or scientists get embryos is therapeutic cloning, which merges a cell (from patient who needs the stem cell therapy) with a donor egg
• Adult Stem Cells: In any living, breathing human, hide in tissues/organs to protect from UV radiation and mutations; they divide and specialise to repair/replace surrounding differentiated cells lost through normal wear/tear, injury or disease
• Common example of Adult Stem Cells: Hemopoietic stem cells, which are found in red bone marrow, these stem cells differentiate into various blood cells (red blood cells, lymphocytes, and platelets)
• Cell differentiation: Process by which a stem cell becomes a specialised type of cell, occurs when some genes are “switched off” and other genes are expressed more, resulting in: changes to the number and type of organelle