Signalling Pathways Flashcards
Explain the Process of Notch Signalling
When delta not bound to Notch - target gene suppressed.
Delta binds to notch, cleavage of Notch fragment called NICD
This migrates through cytoplasm into nucleus.
Binds to RBP - J transcription factor
Resulting in expression of target genes.
Explain the Wnt signalling pathway
Binds to “frizzled” receptor
Initiates dishevelled protein, this then binds to GSKbeta
Allows dissociation of beta- catenin from APC - protein
B catenin travels to nucleus, binds to TCF protein
Causes B catenin to become transcription factor.
Describe the Hedgehog pathway
In absence of hedgehog ligands, pathway turned off by PTCH (Patched), supresses smoothened.
Ligands bind to Patched which degrades Patched.
Removal of Patched allows smoothened to move from intrallular compartment to cell surface
Initiates hedgehog pathway
describe neural induction
takes place just before neurulation
just before and during gastrulation, organizer produces neural inducing signals that act on adjacent endoderm.
Why is Drosophila Melanogaster a model organism?
System of choice for systematic genetic screens of complex biological processes in a multicellular organism.
Excellent for conventional and molecular genetics
Easy to keep, rapid life cycle, range of techniques, in depth analysis possible, cheap! many embryos are available for use
Why is Xenopus Laevis a model organism?
Good for vertebrates!
Large, accesible eggs, easy to manipulate, eggs fertilised outside animal so development is easily followed.
Can microinject molecules into egg, manipulating gene function.
However poorly suited to conventional genetic analysis, long generation time!!
Why is the Zebrafish a model organism?
Recent addition to vertebrate embryonic development. Similar to Xenopus in that eggs are large and accesible, fertiised externally, easy to manipulate.
Transperant for first 2 weeks of life, so microscopes are able to observe individual cell behaviour in real time
Whys is Gallus Gallus (Chick) a model organism?
Good for embryology
Fertile eggs are easily available , develop externally
embryo withstands experimental microsurgery well.
Can be cultured outside of egg
Why is the Mouse (Mus Musculs) a mode organism?
Best model for mammals
Difficult for embryology, as development entirely within mother
Expensive time consuming but good for development genetics
Rapid breeder
Researchers can modify/delete genes using transgenic techniques
Can make conditional mutations - sophisticated
what are adult stem cell properties?
lineage restricted multipotent cells
rare
highly regulated
self renewal
what is a hematopoietic stem cell?
a cell from the blood or bone marrow that can renew itself, and differentiate into a variety of specialized cells. can mobilize out of bone marrow into blood
what experiment displayed the potential of hematopoietic stem cells?
transfusion of a suspension of bone marrow cells into a mouse that had recieved a lethal dose of X - irradiation. mouse would normally have died after being exposed due to lack of blood cells, however transplant of bone marrow cells reconstituted the hematopoietic system and the mouse recovered.
