What are stem cells ?
Unspecialised cells that continually divide and can develop into other types of cells (differentiate)
What are totipotent stem cells ?
They can divide and produce any type of cell
What are the features of topipotent stem cells ?
Only present for a limited time in the first few divisions of a mammalian embryo
During development not all stem cells genes are expressed, so some are not transcribed or translated into proteins
The genes that are expressed lead to synthesis of proteins that determine cell structure and function
Pluripotent stem cells
Embryonic stem cells that can divide in unlimited numbers and develop into most of the body’s cell types
How can pluripotent stem cells be used ?
They can be used to treat human disorders as they differentiate into any body cell
Can get from 4-5 day old embryos that are spare from being used in IVF and the rest of the embryo- ethical concerns
Multipotent stem cells
Adult stem cells that can develop into a limited number of cell types
How can multi potent stem cells be used ?
To replace a variety of different cell types but it is limited
Requires a donation of stem cells from a genetically compatible donor
Unipotent stem cells
Can only differentiate into one type of cell
Examples of uses of embryonic stem cells in medicine ?
Parkinson’s disease: replace lost dopamine neuron’s
Type of one diabetes- generate insulin producing beta cells
Macular degeneration
Spinal cord injury
How are induced pluripotent stem cells produced ?
Take somatic adult cells and infect them with a modified virus. the virus contains genes coding for transcription factors so that the cells become pluripotent
Transcription factors attach to the promoter region of DNA and stimulate RNA polymerase to stimulate transcription
The cells divide and differentiate into the desired cells
Uses of IPS cells
Disease modelling
Create patient specific cells for studying diseases like Alzheimer’s
Adv and dis of embryonic and adult stem cells
Embryonic:
Pluripotent can differentiate into any stem cell
But they only exist for a limited time frame
Adult:
Can use own patient cells-Same genes so less chance of rejection
But difficulty getting donors from other people
Evaluating the use of stem cells in treating human disorders
Benefits:
All stem cell treatments in medicine provide long term treatment as they continuously divide
Stem cells could be used to grow organs to save lives or replace damaged tissue
Bone marrow stem cells are already being used to treat leukemia and have been used to cure HIV
Issues of use of stem cells in treating human disorders
Obtaining embryonic stem cells involves the destruction of an embryo
Cells continuously divide increases the risk of uncontrollable cell division and production of tumours
Non functioning cells must be destroyed which can be very painful and increases chance of infection
