Cellular Differentiation, Stem Cells and Modern Medicine Flashcards
How does an embryo begin?
As a small number of naive, totipotent cells
What does totipotent mean?
A cell than can give rise to all parts of the embryo and adult as well as extra embryonic membranes (placental) in species that have them
What can embryonic stem cells give rise to?
All cell types except trophectoderm (they are pluripotent)
What does pluripotent mean?
A cell (immature or stem) capable of generating all the cells of an embryo with the exception of placenta
What happens to a cell as it develops?
It becomes more specialised and less flexible
When does the restriction of the cell stop?
When it becomes terminally differentiates and can only give rise to the same type of cells
What are the exceptions to cells becoming more specialised and less flexible during development?
Stem cells and germ cells (sperm and egg)
What are the stages of embryo development?
8 cell stage»_space;> Cell polarisation»_space;> Compaction»_space;> Inner, apolar cells cut off»_space;> Blastocyst
What does a blastocyst consist of?
Inner Cell Mass (ICM) which is the embryo and the trophectoderm which is the placenta
What are embryonic cells?
Non-differentiated (pluripotent) and contain genetic information to make any type of differentiated cell. Muscle specific genes are not being transcribed
What happens when the cell becomes a myoblast (determined)?
The cell must now develop into a muscle cell. Certain control genes which code for transcription factors are actuated and so transcription factors are produced.
What happens when the cell becomes terminally differentiated?
The transcription factors are able to turn on other genes to make other transcription factors and other proteins forming a fully functioning cell that plays a role in the organism
What is meant by genomic equivalence?
Differentiated cells contain all the DNA required to build an entire new organism
How are embryonic stem cells obtained?
They are harvested from the inner cell mass (future embryo) of mammalian cells
How do the cells derived from embryonic stem cells compare to the embryo donor?
They are genetically identical
How are induced pluripotent stem cells made?
By reprogramming adult skin cells (pushing it back in time to make and embryo)
What can iPS cells be made from?
Anyone
How would iPS cells be described?
Genetically identical to the source skin cells. As they are also pluripotent, they can generate any cell type.
How do stem cells divide?
Without limit
How are adult (tissue) stem cells described?
Undifferentiated, multipoint cells
What is multipoint?
They can divide to give rise to both stem cells and cells which will go on to differentiate into one or more (but not all) types of functional tissue cells
What are stem cells important for?
Tissues such as skin and blood which need constant renewing
What is a progenitor cell?
A cell which will go on to form specific things
Where are blood stem cells found?
In the bone marrow
What can blood stem cells be used for?
Transplants
What is now a common practice in some countries?
Cord blood banking
What is involved in cord banking?
Stem cell blood isolated from the umbilical cord of newborn babies are kept frozen (banked)
How are umbilical cord stem cells described?
Multipotent as they are immature blood stem cells. They are less restricted than blood stem cells from adults (i.e they can make all blood types)
What can umbilical cord stem cells be used for?
To treat leukaemia and many other blood diseases
What are stem cells important for in modern medicine?
Gene therapy and regenerative medicine
What is gene therapy based on?
The idea that it may be possible to alter the genetic code of an individuals cells
What is gene therapy proposed for?
As a way of correcting single gene disorders
What could happen in gene therapy?
A normal allele could be inserted into the cells of the affected tissue
How could a normal allele be inserted into the cells of the affected tissue?
Virus is one way to deliver genetic material to human cells but CRISPR (gene editing) may also be used
What is regenerative medicine based on?
The idea that pluripotent stem cells can be used to repair or replace damaged organs or tissues
How can pluripotent stem cells be obtained?
They maybe made from skin cells or blood cells from a patient (genetically identical) or matched donors, or from embryos
What can stem cells be encouraged to do?
Differentiate into specific cell types such as neurons, or retinal cells based on their culture conditions
What can be done with differentiated cells?
They can be transplanted into patients
