GED L20 Flashcards
Describe the experiment which led to the conclusion of totipotency of cells & name the scientist responsible
• Separation of 1st 2 blastomeres -> Sea urchin eggs: (Hans Diresch)
- Each cell at the 2-cell stage or 4-cell stage of meiosis are totipotent.
»_space; Cell has capacity to generate totality of cells present in an organism.
Describe what baby hair ligature experiments revealed & how this was done & name the scientist involved.
• Baby hair ligature experiments: (Hans Spemann)
First nuclear transplantation experiments.
Using baby hair to separate 1st 2 cells of frog embryo.
» Both cells develop into entire embryos rather than half an embryo.
If Incomplete separation of cells using hair;
Continuous nuclear division -> one cell
»_space; Develops sufficiently small nucleus to enter other cell via hole
»_space; Other cell (previously not containing nucleus) -> develop into whole
Embryo.
> Illustrate 16 cell stage nuclei are totipotent
(Whole embryo can develop from stage 16 cell.)
Describe the experiment illustrating the natural loss of cell totipotency over time & nam ethe scientist involved
Cloning of frog embryos: (Briggs & King)
Nuclei up to blastula stage could produce entire embryo -> Totipotent.
Nuclei further developed than blastula stage -> Not Totipotent.
»_space; More differentiated cells lose their ability of totipotency over time.
What is the Waddington Landscape Hypothesis?
Waddington Landscape Hypothesis:
Totipotent cells become differentiated
> Once differentiation begins, it cannot be reversed.
> Potency decreases over time.
Describe the first successful cloning experiment of an entire organism & name the scientist involved
Cloning Protocol: (John Gurdon)
Extraction -> Terminally different pigmented cells -> Tadpole epithelia.
> Transplanted into denucleated wild type (pigmented) eggs
-> (Denucleated via UV radiation)
Serial transplantations -> Produced blastula stage embryos
»_space; Died.
Transplant nuclei -> Dying blastula stage embryo -> Into Albino type Eggs
> Repeat several times.
Eventually developed fully formed identical frogs
Define Pluripotency
• Pluripotency:
- Cellular ability / potential -> Differentiate into any type of cell except embryonic / placental cells.
- Cellular ability / potential -> Differentiate into any type of cell from a distinct set of cells.
Define Bipotency
• Bipotency:
- Cellular ability / potential -> Differentiate into any of two particular types of cell.
• Unipotency:
- Cellular ability / potential -> Differentiate into one particular type of cell only.
Define Totipotency
• Totipotency
- Cellular ability / potential -> Differentiate into any type of cell
- Ability / potential of a blastomere -> produce a fully-developed embryo.
Define Unipotency
• Unipotency:
- Cellular ability / potential -> Differentiate into one particular type of cell only.
Describe the first experiment to successfully clone a mammalian blastocyst & name the scientists involved
• Cloning of Mammals -> Dolly the Sheep: (Campbell & Wilmut)
Nuclear Transfer -> Cultured cell line
- Donors:
Eggs -> Scottish Blackface.
» Denucleated
Udder cells -> Finn-Dorset
- Transfer udder cells -> denucleated egg.
- Fused with electric current & cultured
» Development -> Blastocyst
- Transferred to Scottish blackface surrogate
» Birth of Finn-Dorset lamb
> Genetically identical -> Nuclear donor (Udder cells)
Describe the trophectoderm of early mammalian blastocysts
- Trophectoderm:
» Outer layer of cells of a blastocyst.
» Provide nutrients -> the developing embryo, facilitate attachment to the uterine
lining and become part the placenta.
Describe the blastocoel of early mammalian blastocysts
- Blastocoel:
» Fluid-filled, inner cavity of a blastocyst resulting from cleavage of the oocyte after
fertilization.
Describe the epiblast of early mammalian blastocysts
- Epiblast: (Primitive mesoderm)
» Forms embryo proper
» Cell layer -> develops from inner cell mass (accumulation of cells attached to inner
lining of trophoblast) of blastocyst.
» Differentiates -> Ectoderm, mesoderm & endoderm
» Develops -> Extraembryonic membranes.
Describe the hypoblast / primitive endoderm of early mammalian blastocysts
- Hypoblast (Primitive endoderm)
» Forms inner cell mass
» Layer of cells which enclose epiblast / accumulation of cells attached -> trophoblast & separate from blastocoel.
» Develops -> Extraembryonic membranes
Describe the development of development of stem cells using nuclear programming
Treatment of Early Blastocysts / epiblasts -> certain conditions
» Produce permanently pluripotent cells
> Leads -> concept of embryonic stem cells.
Permanently pluripotent blastocysts
»_space; Genetically modified -> Generation of specific cell pathway / lineage
> Grow in culture
> Remove factors ensuring blastocysts remain pluripotent
Describe the basis of knowledge used to enable development of stem cells by nuclear programming
- Extra-embryonic membrane -> Unique to mammals
» Provides nutrients -> Embryo - Early stage blastocysts totipotent
» Dev. -> Extra-embryonic mem & entire organism - Blastocysts -> Not totipotent
» Dev. -> Everything but extra-embryonic mem.
What is the source of pre-implantation embryos / embryonic stem cells?
- Epiblast of pre-implantation embryos / Embryonic Stem Cells
Source of pluripotent stem cells
»_space; Ability to produce all somatic & germ cells -> Except extraembryonic membranes.
»_space; Permanent maintenance -> Pluripotent abilities in culture.
Describe the potency of an epiblast of an early mammalian embryonic stem cell
> > Ability to produce all somatic & germ cells -> Except extraembryonic membranes.
»_space; Permanent maintenance -> Pluripotent abilities in culture.
Describe the uses of stem cells
Uses:
Study of in-vitro development
Transplant -> Blastocysts
»_space; Dev. of genetically modified organisms.
Generation -> Teratomas.
»_space; Benign Tumors
> Differentiate outside normal env.
–> Generate new tissues
-> (No metastasis but can use to predict potential dev. of embryonic stem cells)
Study of disease & organ pathologies
Used -> Drug screening
Development of knockout genes
Growth of organs/tissues
Eg. Eyeball, Parts of Brain, Neurons, Cortex Tissue, Spinal Chords.
- Led to significant replacement of animals in research.
Who was responsible for the development of regenerative medicine methods & what did they do?
(Yoshiki Sasai)
Growth of organs/tissues
Eg. Eyeball, Parts of Brain, Neurons, Cortex Tissue, Spinal Chords.
Briefly describe the method of reprogramming differentiated cells & name the scientist responsible
• Reprogramming Differentiated cells: (Shinya Yamanaka)
Differentiated cells reprogrammed -> return to Pluripotent Embryonic state
» Without use of nuclear transplantation.
»_space; Production -> Induced Pluripotent Stem (iPS) cells
Describe the process of differential cell reprogramming
Process:
- Various solutions of gene mixtures added -> Fibroblasts
» Investigate which mixtures reprogramme cells
> Produce Pluripotent Embryonic cells
What were the results of differential cell reprogramming?
Result:
- Generation of clones -> Induced Pluripotent Stem (iPS) stem cells
» Act like Embryonic stem cells -> iPS
> Cocktail : Klf-4, Sox-2, Oct4, Myc
What are cell reprogramming / iPS cells used for? List some of their benefits.
Uses / Benefits:
- Can use any cell Eg. Skin -> Produce Pluripotent stem cells
» Embryonic stem cells not required -> Ethics
- Produce pluripotent stem cells
» Determine / manipulate development -> specific required cells.
- Produce genetically modified organism
- Used to generate human iPS cells
- Taken from those with disease
» Model diseases in vitro for investigation rather than patient
- Use in transplants
» Production of cells / organs / tissues which are not immunologically rejected.
- Produce iPS cells from patients
» Cell replacement therapies / regenerative medicine.
Describe how successful cell transplant therapies can be performed using iPScells
- Produce iPS cells from patients
» Cell replacement therapies / regenerative medicine.
Eg. Mouse -> Sickle Cell Anaemia
> Isolate skin cells -> Develop iPs cells
> correct mutation in cells / produce new functional cells
> Induce dev. -> haematopoetic cells (used to generate RBCs / stem cells)
> Transplantation back into organism can cure disease.
Do cells lose genetic material as they develop?
• Cells do not lose genetic material during development
What are the main points derived from the Waddington Landscape Hypothesis?
• Waddington Landscape Hypothesis:
Totipotent cells become differentiated
> Once differentiation begins, it cannot be reversed.
> Potency decreases over time.
Describe cell potency
• Cell Potency:
- Ability of a cell to differentiate into other types of cell.
Describe induced pluripotency
• Induced Pluripotency:
- Pluripotency of a cell derived as a result of reprogramming any non-pluripotent cell into an Induced Pluripotent Stem Cell.
What are embryonic stem cells derived from?
• Embryonic Stem cells -> Derived from Epiblast of pluripotent blastocysts / pre-implantation embryos.
What are the uses of iPS cells?
• Uses -> iPS cells:
- Regenerative medicine
- In-vitro study of disease-causing cells
- Genetic modifications
- Transplantations
- Growth of tissues / organs
- Production of specific required cells -> Use in medicine
- Cloning
- Study of disease & organ pathologies
Etc.
Who was the first scientist so illustrate totipotency of 2-stage cell embryos in sea urchins?
- Hans Driesch
|»_space; First to show each cell of a two-cell stage sea urchin is totipotent
Who used baby hair ligature experiments & illustrated totipotency in blastomere cells up to the 16th stage?
- Hans Spemann
»_space; Used baby hair to constrict embryos and show that blastomeres in salamander
embryos up are totipotent up to 16 cell stage
Who was the first to successfully transplant nuclei into eggs?
- Briggs and Kings
|»_space; First to successfully transplant nuclei into eggs
Who was the first to clone an entire organism?
- John Gurdon
|»_space; First to clone an animal
Who was the first to clone a mammal?
- Campbell and Wilmut
|»_space; First to clone a mammal
Who was the first to induce pluripotency in adult cells without nuclear transplantation?
- Shinya Yamanaka
|»_space; First to induce pluripotency in adult cells without nuclear transplantation
