T3L10/11 Stem Cells Flashcards
What is a totipotent stem cell
A stem cell that can differentiate into any type of human cell
What is a pluripotent stem cell
Stem cells that can differentiate into every type of human body cell excluding extra-embryonic cells such as placental and umbilical cells
What are multipotent stem cells + give examples
Stem cells from adult tissues that can only specialise into certain types of cells.
Example: bone marrow stem cells
Describe potency of stem cells in an early embryo
After undergoing three divisions all embryonic cells are totipotent
Describe the potency of stem cells in a blastocyst
Outer cell layer will from placenta
Inner mass of cells will form the embryo - these cells are pluripotent
What are mesenchymal stem cells
Multipotent adult stem cells that are found in multiple tissues e.g fat tissue
Why does it take us longer to recover from injury as we get older
Number of stem cells we have decreases so it takes longer to replace the damaged muscle/bone/cartilage
Explain how stem cells become specialised
1 Stem cells contain the full genome for an organism
2 Stem cells receive a stimulus that activates certain genes
3 mRNA is transcribed from the active genes
4 mRNA is translated at the ribosomes
5 the proteins produced modify the cell, determining its structure
6 these changes cause the cell to become specialised
What is potency in plants like
All cells remain totipotent throughout their lifetime
Plants can de-differentiate and then re-differentiate into a completely different plant
How can plant stem cells be cloned
Small piece of plant placed on agar gel with nutrients in
Cells then divide to form a mass of undifferentiated cells
These cells can be made to differentiate and form embryos
These embryos can be grown into plants that are genetically identical
What important technique is involved in growing plants cultures
Aseptic technique
What are the two types of stem cells that can be used in medicine and what are the differences between them
Embryonic stem cells and Bone marrow stem cells
Embryonic stem cells have the ability to differentiate into any type of cell whereas Bone marrow stem cells are multipotent and can differentiate into different types of cell
Where do stem cells come from for medical uses
Embryonic stem cells come from ‘spare’ embryos from IVF clinics
Bone marrow stem cells are collected from bone marrow from healthy people and donated
At what stage are embryonic stem cells from
Blastocyst - main cell mass
What biological issues can arise from the use of donor stem cells and how can this be combatted
Rejection
so
Immunosuppressant drugs
What is one way to overcome the risk of rejection of stem cells
Use bone marrow stem cells from the patient themselves
Name advantages of using embryonic stem cells
They can develop into any type of specialised cell
Name the disadvantages of using embryonic stem cells
- Embryonic stem cells can only be used up to 14 days after fertilisation
- Some have ethical issues based on religious objections - is life destroyed when the embryo is discarded?
- Risk of rejection
Name the advantages of using bone marrow stem cells
- Cells are obtained from body (no ethical issues as patient can consent)
- Simple low-risk operation
-Lower risk of rejection if own patient’s stem cells are used
Name the disadvantages of using bone marrow stem cells
There are a limited number of different type of specialised cells that embryonic stem cells can becom e
Describe how therapeutic cloning works
Patient needs stem cell treatment
Donated Ovum is denucleated
Somatic diploid cell from patient denucleated
Nucleus from patient cell placed into ovum
Zygote like diploid cell identical to genome of patient
Cell undergoes stimulated mitosis to produce a blastocyst
Stem cells harvested from blastocyst to be used in treatment
What does the law say about therapeutic cloning
Embryos must be destroyed after 14 days
What are the benefits of therapeutic cloning
Animal ova can be used instead so process is not limited by human supply
No risk of rejection
No need for immunosupressants
What does iPSC stand for
induced Pluripotent Stem Cells
Describe how iPSC works
Use of transcription factors activates certain genes so that somatic cells dedifferentiate
Cell reverts to pluripotent state - stem cells available for treatment
Describe benefits of iPSCs
No risk of rejection or ethical issues
Can differentiate into all somatic cells
What is HFEA
Human fertility and embryology authority
Determine laws and regulation on use of human embryos in medicine and research
Name examples of laws around embryology
Embryos may be used for research on fertility, misscarriage, gene abnormalities and contraception etc
Embryos must be discarded within 14 days
Since 2007 human-animal hybrid embyros are illegal to be used
No reproductive clonign
What is the relationship between parliament and HFEA in terms of new laws and regulation
Parliament creates new laws
but
Regulatory authorities like HFEA advise based on research and peer knowledge
