invertebrate model systems Flashcards
how does transcription vary in mammals and other non- mammalian vertebrates
it begins much earlier in mammals. this is because is encodes extraembryonic tissue which is essential for development
when does zygotic transcription occur in non- mammalian vertebrates
at the midblastula phase. it comes from the incorporation of growth phases 1 and 2 into the cleavage cycle
what are the two types of specification
autonomous- where specification is caused by the asymmetrical distribution of maternal molecules, and conditional- where specification is induced by signals from neighbour cells
what is karyokinesis
division of the nucleus
what is cytokinesis
division of the cytoplasm
where do micromeres form and why
at the bottom of the zygote. this is because there is dishevelled RNA present which induces transcription via the Wnt pathway which would otherwise be repressed
what do micromeres do
they have complete control of skeletal formation. they also induce other cells to change fate to form recognisable larva
what are double negative gates and how is the Wnt pathway an example of this
repression of a repressor results in activation of. in the Wnt pathway dishevelled represses GSK which normally represses beta catenin, so beta catenin is active and induces transcription
what is a feed forward circuit
A activates B and C, B activates C. it is a method of amplification and ensures development only moves in the forward direction
what is the mechanism of gastrulation
skeletal mesenchyme cells lose affinity for the hyaline layer (bottom) and blastomere cells (adjacent) and increase affinity for the basal lamina (top)
how does rudiment degeneration occur in sea urchins
nodal induces the generation of the rudiment on the right hand side of the embryo. only the left rudiment develops into an adult
why is C.elegans a good model organism
it is self fertilising, cellular development is invariant and all genes have a known function
how does asymmetry form in nematodes
Par2 enters the posterior cortex and Par3 and Mex5 is displaced to the anterior
what are the two initial cells forming in the nematode
AB cell and P1 cell. the P1 cell will divide to from the EMS cell (somal) and P2 (will eventually differentiate to Z cells which are germ cells
through what mechanism do germ cells from in nematodes
a double negative gate. Par2 inhibits Mex5 which allows PIE1 to be activated. Par3 in AB cells does the opposite
