EDEXCEL UNIT 2

STEM CELLS

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Un undifferentiated cell of a multicellular organism which is capable of giving rise to indefinitely more cells of the same type, and from which certain other kinds of cell arise by differentiation*.

*Differentiation- The process by which a cell becomes specialised ;

 

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Totipotent stem cell

1. totipotent (stem cells) can give rise to {all / any / 216} cell types / eq ; .

2. (stem cells) are {undifferentiated / unspecialised} / eq

3. can keep dividing / eq ;

4. only present in early life of embryo ; MORULLA -32 CELLS

5. no genes switched off ;

 

Pluripotent stem cell

1. Pluripotent (stem cells) can give rise to {all / any} cell types / eq ;

2. EXCEPT extraembyronic cells ;

3. UNTIL BLASTOCYSTS STAGE

 

Multipotent stem cell

1. body tissues of an adult e.g bone marrow ;

2. simple operation but discomfort to patient ;

3. needle into centre of a bone ;

4. small quanity of bone marrow removed ;

5. idea that adult stem cells {are not flexible / are limited in use / eq} ;

 

Location of stem cells

1. Embryo – differentiate into all cells needed to form a fetus;

2. Adult tissues e.g. bone marrow ;

 

Embryonic stem cells

• Obtained from early embryos

• Embyros created in IVF lab / explained

• Stem cells removed after 4-5 days

• Embryos destroyed ;

• idea that embryonic stem cells can develop into {all / any / 216 / eq} cell types ;

• more likely to cause immune rejection than {adult / somatic} stem cells ;

• totipotent until blastocyst phase (where the cells are pluripotent) ;

 

Benefits/Medical uses

1. Replace damaged tissues (in diseases) ;

2. credit example e.g. nerve tissue for spinal cord or heart tissue for heart-related diseases ;

3. idea of saving many lives e.g. growth of organs for those waiting for transplants ;

4. idea of quality of live being improved e.g. replacing damaged cells in eyes in blind people ;

 

Ethics

1. Destructed embryos were viable ;

2. idea of ‘right to life’ ;

3. stem cells from unfertilised embryos have fewer objections ;

4. arguments that only adult stem cells should be used because there are no embryos destroyed ;

5. however adult stem cells are limited in use ;

 

 

Regulatory authorities

1. Proposals of research are examined to see if they’re carried out for good reason ;

2. Licensing/monitoring centres ensures that fully-trained staff carry research out ;

3. Guidelines / codes of practice to ensure scientists are working in a similar manner ;

4. Monitoring developments in research to ensure any changes are regulated and guidelines are up-to-date;

5. Providing advice/information to the government and professionals to promote the science involved in the research, and aid society in understanding the benefits