quiz 4 Flashcards
gastrulation
early formation of different germ layers
blastocyst
inner mast cell - develops into outer layer (tropoblast and embryo) - becomes placenta in mammals
totipotent vs pluripotent
totipotent - can create a complete organism (placenta included)
pluripotent- cant
epigenetics
how a cell remembers what it should become based off of changes of structure of genome that permits certain genes to be opened or closed
1. combination control
2. cell memory
morphogen
long-range inductive signalling that exert graded effects (varies by conc)
AV axis
animal vegetal
-internal vs external
AP axis
anterior posterior
-head vs tail
DV axis
dorsal ventral
-back vs belly
when is AP axis determined
prior to fertilization (due to bicoid)
bicoid- how does it give rise to AP axis
at anterior pole, diffusion gradient away from point gives rise to AP axis
mechanisms of pattern formation- AP axis
-bicoid
-gap genes
-pair-rule
-segmental polarity
bicoid role, regulation and what happens if mutated
-gives head and tail (AP)
-prior to cellurization
If mut: lose segmentation
gap gene role, regulation and what happens if mutated
-subdivides core segments
-active when bipoid is low
If mut: gets head, tail and only one area in between
pair-rule role, regulation and what happens if mutated
-divides ares defined by GAP
(1/2 of each segment under influence of pair-rule)
-gap genes drive expression of pair role (co-exressed with Gap)
If mut: no segmentation of segments
segmental polarity genes (ie. Hedgehog) role, regulation and what happens if mutated
-gives polarity to each segment, so that 1/2 of each segment is not a mirror image of whats next to it
-pair-rule (?) further divides segments, drives segment polarity genes
If mut: all segments are the same
what do segmental genes do
control drosophila segmentation along AP
subdividing of drosophila embryo
-one cell makes and secretes wnt, -acts on neighbouring cell thru effector protein (engrailed)
-engrailed signals for synthesis and release of hedgehog
- hedgehog further promotes release of WNT
-after 3 dcell divisions along AP engrailed is stabalized and no longer needs WNT
hox
locks in and stabalizes patterning
what is hox controlled by and what 2 complexes does it function thru
WNT and HH
Bithorax complex (abdominal and thoracic)
Antennapedia complex ( thoracic and head)
loss of hox
cells that are all alike, can develop segments at wrong place
sequential gene activation
posterior genes inhibit anterior
-if most posterior gene is on, no other ones are
-changes in chromatin structure and sequential opening/closing of heterochromatin
trithorax
keep chromatin open once hox genes are on (most posterior gene dominant)
polycomb
keep chromatin closed in regions where hox is not expressed
mutation is esc gene
blocks polycomb, all chromatin pen and all hox genes on