CGE: Stem Cells Flashcards
Totipotent stem cells
Can mature into any type of body cell.
All specialised cells come from what?
Stem cells
Where can stem cells be found?
In the embryo and in some adult tissues.
Where are totipotent stem cells present?
Only present in mammals in the first few cell divisions of an embryo.
What happens to totipotent stem cells in mammals after the first few cell divisions?
They become pluripotent.
Can still specialise into any cell in the body, but lose the ability to become cells that make up the placenta.
Stem cells in adult mammals are either…
Multipotent or unipotent
Pluripotent stem cells
Stem cells that can specialise into any body cell, but have lost the ability to differentiate into cells that make up the placenta.
Multipotent stem cells
Stem cells that can differentiate into a few different types of cell.
Unipotent stem cells
Stem cells that can only differentiate into one type of cell.
Can mature into any type of body cell.
Totipotent stem cells
Stem cells that can specialise into any body cell, but have lost the ability to differentiate into cells that make up the placenta.
Pluripotent stem cells
Stem cells that can differentiate into a few different types of cell.
Multipotent stem cells
Stem cells that can only differentiate into one type of cell.
Unipotent stem cells
Describe the process of stem cells becoming specialised:
- Under the right conditions, some genes are expressed and others are switched off.
- mRNA is only transcribed from specific genes.
- mRNA from these genes is translated into proteins.
- Proteins modify the cell - determine the cell structure and control cell processes.
- Changes to the cell produced by proteins = cell is specialised.
Give an example of a cell becoming specialised:
- Stem cell produces new cell where the genes for haemoglobin production are expressed.
- Other genes, eg. those involved in removing the nucleus, are expressed too.
- Many other genes are not expressed.
- Specialised red blood cell forms.
Cardiomyocytes
Heart muscle cells that make up the heart tissue.
What was previously thought about cardiomyocytes?
What has new research shown?
Previously thought they could not divide to replicate themselves.
Research has suggest hearts have some regenerative capability.
What is the main use of stem cells?
- Stem cell therapy to treat disorders.
What diseases do stem cell therapies already exist for?
Diseases affecting the blood and immune system.
What does bone marrow contain?
Stem cells that can become specialised to form any type of blood cell.
What are bone marrow transplants used for?
To replace the faulty bone marrow in patients that produce abnormal blood cells.
What has stem cell therapy been successfully used for?
To treat leukaemia (cancer of the blood or bone marrow) and lymphoma (a cancer of the lymphatic system).
What is SCID?
Severe combined immunodeficiency.
A genetic disorder that affects the immune system.
How does SCID affect an individual?
- Poorly functioning immune system as white blood cells are defective.
- So they can’t defend the body against infections by identifying and destroying microorganism.
- Leaves them extremely susceptible to infections.
What is the treatment for SCID?
- Bone marrow transplant replaces faulty bone marrow with donor bone marrow that contains stem cells without faulty genes.
- These differentiate to produce functional white blood cells - can identify and destory invading pathogens = immune system functions properly.
What uses of stem cells are scientists researching?
- Spinal cord injuries - replace damaged nerve tissues
- Heart disease and damage to heart .
- Bladder conditions - grow new bladders which can replace diseased ones.
- Respiratory diseases - donated windpipes can be stripped to collagen structures and covered with tissues generated by stem cells.
- Organ transplants - organs can be grown from stem cells to provide new organs for people on donor waiting lists.
What are the two main benefits of stem cells?
- Could save many lives - eg. could be used to grow new organs for people awaiting transplants.
- Could improve quality of life - eg. replace damaged cells in blind patients.
What are the 3 main potential sources of human stem cells?
- Adult stem cells
- Embryonic stem cells
- Induced pluripotent stem cells (iPS cells)
Where are embryonic stem cells obtained from?
How?
Obtained from body tissues of an adult, eg bone marrow.
Obtained through a simple operation - little risk but lots of discomfort.
What is the main limitation of adult stem cells?
Not as flexible as embryonic - they’re multipotent.
Where are embryonic stem cells obtained and how?
From embryos at early stage of development.
- In vitro fertilisation - fertilises egg cells outside the womb.
- At approx. 4-5 days old stem cells are removed.
- Embryo destroyed.
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What type of stem cells are embryonic stem cells?
Pluripotent
What type of stem cells are adult stem cells?
Multipotent
What are iPS cells?
Induced pluripotent stem cells.
Created by scientists in the lab by ‘reprogramming’ specialised adult body cells so that they become pluripotent.
How are adult body cells turned into iPS cells?
- Made to express a series of transcription factors that are associated with pluripotent stem cells.
- Caused by transcription factors.
How can transcription factos be introduced to the adult stem cells to help them become iPS cells?
- Infection with a specially-modified virus.
- Virus contains genes coding for transcription factors within its DNA.
- Upon infection, these genes are passed into adult cell’s DNA.
- Adult stem cell can now produce transcription factors.
Why is the use of iPS cells currently limited?
More research is needed to test the similarity to true pluripotent embryonic stem cells.
What are some ethical issues surrounding stem cell usage?
- Destruction of an embryo - could become a fetus if placed in womb.
What would be a solution to the ethical issues surrounding the use of embryonic stem cells?
iPS cells - can be as flexible as embryonic cells but don’t result in the destruction of an embryo.
How could iPS cells become even more useful?
If they are made from a patient’s own cells - would be genetically identical to patient’s cells and so wouldn’t reject.
