stem cells

what are stem cells?

1. Undifferentiated, unspecialised cells

2. Can differentiate into various specialized cells upon stimulation by molecular signals

3. Capable of undergoing extensive proliferation & self renewal through mitosis

   
   

what does Undifferentiated, unspecialised cells mean? give examples

With NO tissue-specific structure for specific functions

E.g: hemoglobin, myosin 

Specialized cells: muscle cells, RBC, nerve cells

when the cells receive molecular signals, what happens?

Molecular signals:

• Able to switch ON/OFF genes

what does extensive proliferation mean?

cell’s ability to divide infinitely (mitosis)

why do the cells divide infinitely?

• Can express their telomerase gene which lengthens the telomeres of their chromosomes 

• prevents them from reaching critical length

• prevents the cell from undergoing apoptosis

what does self-renewal by mitosis mean?

divide + produce a cell identical to itself

what are the 2 type of division that stem cells undergo?

1. symmetrical

2. asymmetrical

what does symmetrical division mean?

• producing 2 daughter stem cells that possess the same developmental and differential potential as parent cell

 why is this important to produce more stem cells of the same differential potential?

• Maintains a pool of stem cells for further division

what does asymmetrical division mean?

1. 1 daughter stem cell 

(identical to parent)

• Provide a constant pool of stem cells 

2. 1 daughter stem cell

(progenitor)

• increase/renew population of specialized cells in specific tissues

how does asymmetrical division occur?

molecular signals

Q function?

1. Self-renewal to ensure a constant pool of stem cells

2. Growth and development

3. Differentiate into specialized cells to regenerate/replace cells lost due to cell death/injury 

what happens if a stem cell division results in 2 progenitor cells all the time?

• No longer be self-renewal and all stem cells will eventually deplete  

 what is the difference between genome of a stem cell and a specialised cell?  

• There is NO difference between the genome of a stem cell and a specialised cell  

What accounts for the difference in characteristics? 

• The difference in characteristics is as a result of differential gene expression  

 suggest how stem cells are able to differentiate into specialized cells upon receiving molecular signals such as hormones/growth factors?

Molecular signals may activate/shut down expression of specific genes that result in the synthesis of tissue specific structures that enable these specialised cells to perform certain functions

what are the different potential of stem cells?

1. totipotent

2. pluripotent

3. mutlipotent