L26 Flashcards
What are Somites?
Forms vertebral structures and back muscles –> move after some times because the cells have specialised
What do the cells look like at the 8 cell stage?
Rough, all the cells are the same
What would happen if you were to take a cell out from the 8 cells?
The cells can compensate for the loss because all the cells are the same at this point
What happens if you split the 8 cells into 2 4cell halves
Formation of twins
What happens during cell polarisation?
The cells form a distinct structure with a gap in the middle, adhesions of the cells alongside each either and formation of microvilli on the outside
Compaction
The cells join together asymetrically and there is asymmetric division of cells that form an outer and inner layer
Goes from rough to smooth
What are the apolar cells?
The inner cells that are cut off from the uterine surroundings and take a different developmental path i.e they form the blastocyst (embryo)
Trophectoderm
The formerly polar layer, its the embryos contribution to the placenta
Totipotent
Naive cells, found during the 8 stage development, can turn into any cell including trophectoderm
Pluripotent
The inner embryonic cells, can transform into any cell EXCEPT trophec
Terminally differentiated
When the cell is specialised
*Can only do 1 job
*When divides, daughter cells are identical
Exception to differentiation
Need to keep some cells aside for passing on info and growth
*Germ cells don’t differentiate
*Stem cells, somewhat differentiated but not so much, can still form a few different cell types (found in renewal tissue and provides us with new cells)
The more specialised a cell is
The less flexible
Why don’t embryonic precursor cells not produce a specific protein
Its because the specific genes are turned off eg myoD
If gene is not being transcribed, no protein is formed
What happens to precursor cells by chance?
By chance, forms a specific cell eg muscle cell
*Determined as it can change if we mess with it but otherwise it activates other muscle genes that it would work with
What does the Master regulatory gene produce
Protein MyoD protein that is a transcription factor
*goes back into nucleus and binds on regulatory areas on genes and turns them on/off
MyoD protein does…
Goes to its own gene and keeps the gene to produce myoD on
*Then more MyoD goes to other genes and turn them on, they produce their own transcription factors that bind to other regulatory genes –> myosin and cell-cycle blocking
What is cell cycle blocking?
The cell stops dividing into different types and specialises due to the transcription factors turning on specific genes
How do muscle fibres form?
Fuse into cincitia, no obstruction of the outer discs of cell
Cloning experiments
*Pluripotent nuclei from a frog embryo taken an implanted in an Enucleated frog egg
- As pluripotent, was able to develpp into embryo
*intestinal nucleus implanted in Enucleated frog egg, most didn’t develop but some did, could be because the specialised cell couldnt revert back to embryonic stage
How is the nucleus in a frog egg destroyed
Using UV light
What did the cloning experiments prove?
That all DNA is retained in adult cells
How are embryonic stem cells made?
*Harvested from blastocyst from mammalian embryos
*Cells are pluripotent and under the right conditions and cues + chem condition, it can be transformed into any tissue/cell that we want
*Identical to donor but can be tissue matched
What are Induced Pluripotent Stem Cell (iPS)
*Turn on genes that make a cell embryonic
*Using adult stem cells –> make embryonic –> pluripotent using flibroblasts from skin or blood cells
*Removes the ethical dilemma
*Cell tissue matched to you and can be made into any cell type
Adult STEM cells
*Renews tissue
*Divides without limit - dont live very long
*Undifferentiated multipotent cells - only divide into 2-3 different types based on their specialised area
*Divides asymmetrically to give rise to stem cells and cells that will go on to differentiate into specialised tissue
Umbilical cord STEM cells
*Full of immature STEM cells
*Frozen with dry ice or Nitrogen
*Multipotent, less restricted
*Treat siblings and matched patients
How do STEM cells divide?
*Divides to give one STEM and one progenitor, which divides until it forms fat/bone/blood cells
*Can divide to give only progenitor cells but thats the end of the STEM cell
Blood STEM cells aka
Haematopoietic STEM cells in bone marrow
Blood replaced every 6 weeks
What kind of gene therapy is usually used?
Plasmid - temporary
Integrated gene therapy
*Monogenic diseases where both copies of the allele are broken
*Use a virus vector to inject a healthy copy of gene into the targeted cells which gets integrated with DNA and becomes healthy
*Random and can go wrong
Regenerative medicine
*Pluripotent STEM cells can be used to repair or replace damaged tissue
*made from stem cells of patient, donor or embryo
*Grow the organ/tissue in a lab and
