Gene Expression- Stem Cells Flashcards
Where do all specialised cell types originate from?
Stem cells
What are stem cells?
Unspecialised cells that can develop into other types of cell
What do stem cells divide to do?
To become new cells which then become specialised
Where are stem cells found?
In the embryo and in some adult tissues
What are totipotent cells?
Stem cells that can mature into any type of body cell in an organism
When are totipotent cells present in mammals?
Only in the first few cell divisions of an embryo
What do embryonic stem cells become after the first few cell divisions?
Pluripotent
What are pluripotent cells?
Can still specialise into any cells in the body but have lost the ability to become the cells that make up the placenta
What are the two types of stem cells present in adult mammals?
Multipotent and unipotent
What are multipotent cells?
Able to differentiate into different types of cell
What are unipotent cells?
Can only differentiate into one type of cell
Why do stem cells become specialised?
They all contain the same genes but during development, not all of them are transcribed and translated
What happens to genes under the right conditions?
Some genes are expressed and others are switched off
What happens to mRNA?
It is only transcribed from specific genes and the mRNA from these genes is then translated into proteins, and these proteins modify the cell by determining the cell structure and controlling cell processes
Why does a cell stay specialised?
Changes produced by proteins are difficult to reverse
What are cardiomyocytes?
Heart muscle cells that make up a lot of tissues in our hearts
What do some scientists now think about cardiomyocytes?
Old or damaged cardiomyocytes can be replaced by new cardiomyocytes derived from a small supply of unipotent stem cells in the heart
Do stem cell therapies currently exist?
Yes for some 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
How can bone marrow transplants be used?
To replace the faulty bone marrow in patients that produce abnormal blood cells- stem cells in transplanted bone marrow divide and specialise to produce healthy blood cells
How have stem cell therapies been successfully used?
To treat leukaemia and lymphoma as well as genetic disorders such as sickle-cell anaemia and severe combined immunodeficiency
How could stem cell therapies treat spinal cord injuries?
Stem cells could be used to replace damaged nerve tissue
How could stem cell therapies treat heart disease and damage caused by heart attacks?
Stem cells could be used to replace damaged heart tissue
How could stem cell therapies treat bladder conditions?
Stem cells could be used to grow whole bladders which are then implanted in patients to replace diseased ones
How could stem cell therapies treat respiratory diseases?
Donated windpipes can be stripped down to their simple collagen structure and then covered with tissue generated by stem cells and this can then be transplanted into patients
How could stem cell therapies treat organ transplants?
Organs could be grown from stem cells to provide new organs for people on donor waiting lists
What are 2 benefits of using stem cells in medicine?
- Could save many lives as stem cells could be used to grow organs for those people awaiting transplants
- Could improve quality of life for many people
What are the 3 main potential sources of human stem cells?
Adult stem cells, embryonic stem cells and induced pluripotent stem cells (iPS cells)
Where are adult stem cells obtained from?
Body tissues of an adult
When can adult stem cells be obtained?
In a relatively simple operation with very little risk involved but with quite a lot of discomfort
How are adult stem cells not as flexible as embryonic stem cells?
They can only specialise into a limited range of cells, not all body cell types
Where are embryonic stem cells obtained from?
Embryos at an early stage of development
Where are embryos created?
In a laboratory using in vitro fertilisation
What happens once the embryos are approximately 4 to 5 days old?
Stem cells are removed from them and the rest of the embryo is destroyed
What are embryonic stem cells?
Pluripotent because they can divide an unlimited number of times and develop into all types of body cells
What are iPS cells?
Created by scientists in a lab- involves ‘reprogramming’ specialised adult body cells so that they become pluripotent
Why are iPS cells made?
To express a series of transcription factors that are normally associated with pluripotent stem cells
What is one of the ways these transcription factors can be introduced to adult stem cells?
By infecting them with a specially-modified virus that has the genes coding for the transcription factors within its DNA
What are the ethical issues surrounding embryonic stem cell use?
- Involves destroying an embryo that could potentially become a fetus if placed in a womb
- That embryo has a right to life
- Scientists should only use adult stem cells because their production doesn’t create destruction
