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Explain how a single-cell zygote is able to develop into a multicellular organism made up of various different tissues and specialised cells.
- -All cells in the body except the gametes are genetically identical/ contains the same genes
- -Different set of genes are expressed only at various stages of the body's development
- -During differentiation into specialized cells, certain genes are silenced while others are expressed
- -Each cell's type and function is thus determined by the protein it produces.
Explain how embryonic stem cells can be manipulated for therapeutic applications.
- -Genetic manipulation can be carried by the random incorporation of DNA within the genome by various methods such as electroporation.
- - The stem cells can be cultured under specific conditions using appropriate growth factors and chemicals.
- -This is followed by the growth and differentiation of cultured embryonic stem cells into the desired cell types, which can then be transplanted back into the tissue of the patient.
State the characteristics of a stem cell.
- 1) They are unspecialised as there is an absence of tissue-specific structures that allow it to perform specific functions
- 2) It is able to proliferate unlike normal cells
- 3) It able to undergo differentiation to develop specialised cells when triggered by intracellular and extracellular signals.
Define the term stem cells.
Stem cells are cells that are unspecialised that can divide continually and can diffferentiate into specialised cells of one or more types under appropriate conditions.
Define the following terms.
i) Totipotent stem cells
i) Totipotent stem cells are cells that retains the complete set of genetic information and have the potential to become any cell type in the body including any cell of the extraembryonic membranes
ii) Differentiation is a process whereby stem cells, which are unspecialized, developed into specialized cells which perform specific function.
Explain the differences of multipotent and pluripotent stem cells and give an example of each type of cell.
-Multipotent stem cells have a lower potential development
compared to a pluripotent stem cell where it can differentiate into a limited number of cell types
while pluripotent stem cells can develop into any cell type except for the cell of the extraembryonic membrane.
- -Multipotent : Adult or Umbilical stem cell
- -Pluripotent : Embryonic or Fetal stem cell
Describe the two different embryonic stem cells and state their functions.
- 1) Early embryonic stem cells-obtained from the zygote and the first 4 cells after cleavage and is totipotent in nature.
- Functions: give rise to all cells in the body of the organism
- 2) Blastocyst stem cells - obtained from the inner cell mass of the blastocyst and is multipotent in nature
- Function: Give rise to all cells in the 3 germ line (ectoderm, mesoderm and endoderm)
The diagram above shows a human blastocyst. Name the structures A,B and C.
- A: Trophoblast
- B: Blastocoel
- C: Inner cell mass
Describe how the blastocyst stem cells can be used to produce liver cells after the inner cell mass is extracted from the blastocyst.
- - The inner cell mass is then transferred into a culture dish containing a culture medium.
- - The medium contains nutrients that provide nourishment for the cells as well as growth factors that causes the stem cells to differentiate into liver cells.
- - The inner surface of the culture dish is coated with embryonic connective tissue cells to give the inner cell mass a sticky surface to attach to and release important nutrients and hormones.
- - The stem cells will continue to proliferate and subculturing is carried out.
Define adult stem cells and state their function.
- -Adult stem cells are undifferentiated cells found among differentiated cells in a tissue or organ which can renew and differentiate to yield major specialised cell types of tissue or organ.
- -The primary role of adult stem cells in living organism is to maintain and repair the tissue in which they are found.
State where the hematopoietic stem cells are located and their function.
They are found in the bone marrow and they function to give rise to all types of blood cells.
What does the term "differentiated cells" mean?
They are cells that have specialized properties and functions, and have lost the ability to generate cells of other types
Describe the unique features of the neural stem cells.
They are multipotent stem cells which retain the complete set of genetic information and have the potential to differentiate into limited range of cell types.
State the process shown above.
Other than obtaining embryonic stem cells from embryos, what are the altenative ways to obtain these cells?
- 1) Decreased embryos
- 2) Nondestructive biopsy (obtaining the cells from 8 cell stage)
- 3) Bioengineered embryo-like artifacts
- 4) Dedifferentiated somatic cells