C1-HC2 Flashcards
Name 3 germ layers and what they can be turned into:
- Ectoderm: nerve, skin
- Mesoderm: skeletal, blood, bone
- Endoderm: pancreatic, lung, liver
(- Germ cells: sperm, egg)
The oocyte is surrounded by the … & ….
The oocyte (in the follicle) is surrounded by the zona pellucida (protection) and the cumulus cells (they communicate with the oocyte and this is important for the maturation of the oocyte; so it can be fertilised).
Eggs are located (not made!) in ovaries.
The oocyte is large and immobile (can only move passively), sperm cells are small and mobile.
What is 1 diploid cell turned into in men and woman?
Meiosis
Men: 1 diploid cell –> 4 functional sperm cells are formed
Women: 1 diploid cell –> 1 functional oocyte and 3 other cells (polar bodies; not fertilizable) are formed. During the metaphase II, the oocyte is being ovulated.
In haploid sperm cells histones are replaced by …
In haploid sperm cells histones are replaced by protamines.
Normally the DNA is wrapped around the histones, but that makes is relatively big. Protamines are smallers and lie inside the helix of the DNA to give structure.
pre-implementation genetic testing=
Practical use: when you think the embryo might have a genetic disease (e.g. A mutation caused by the parents which are carriers). With IVF embryos you can remove the cell and analyse it. If there is a mutation, it can be decided not to put the embryo in the mother. If it is healthy you can put it in the mother. This is called pre-implementation genetic testing.
Cdx2 is important for formation of …
Oct4 for the formation of …
Cdx2 is important for formation of trophectoderm.
Oct4 for the formation of pluripotent inner cell mass cells.
In second linear segregation, the inner cell mass is differentiated into epiblast cells and hypoblasts cells;
- High [Nanog] > the cells become ... - High [Gata6] > cells become ...
- High [Nanog] > the cells become epiblasts (important transcription factor for stem cells).
- High [Gata6] > cells become primitive endoderm or hypoblasts.
Just before the embryo implants in the womb the desicion is made.
Flexible; cells can interchange later regardless of being exposed to high levels of either Nanog of Gata6.
FGF signalling is immportant to activate Gata6 pathway.
Testing pluripotency of cells:
Testing pluripotency of cells: chimaera formation. You inject the pluripotent cells in the mouse. If the cells are indeed pluripotent, than they will connect. This results in a different coat colour of the mouse. White is the host embryo. Result: different coat colours, than indeed pluripotent cells.
Gastrulation=
Gastrulation: the definitive formation of endoderm, mesoderm, and ectoderm.
Two scenarios for the formation of primordial germ cells (PGC’s):
- Preformation: a structure in the cytoplasm (mitochondrial RNA molecules) will determine which cells become germ cells. C. Elegans and fruit fly > no system, because all cells are preprogramed and just follow that path. In the first division you can already see which cells become germ cells
- Epigenesis: in mammals all pluripotent cells have the capacity to form germ cells (and iPSCs). Growth factors from the extoderm are sent. Cells that receive the growth factors become germ cells. The growth factors will never reach some part of the blastocyst. Mouse > there is a structure and the cells that inhibit, will form germ cells.
Hox genes:
Some animals are clearly segmented. Mammals are also segmented; look at the spinal column. Homeobox genes are essential for anterior-posterior identity. Example: a fruit fly formed front legs instead of antenna due to having a mutant gene. Homeobox genes are expressed sequentially according to their order in the Hox complex. Mammals also have these genes (it occurs in 4 clusters). These genes are located in a row on the chromosome. The location on the chromosome determines the location on the body. 3’ more to the head and 5’ more to the back. It’s also important for the formation of limbs (arms, shoulders, fingers).
