l14 Flashcards
the products of maternal effect genes form _______ that define the AP axis
long range gradients
as the embryo is a synctium, only a single _______ is needed for this morphogen system
transcription factor
this graded information is translated into more _____ of zygotically-expressed ___ whose effects are ____ range
discrete blocks
gap genes
short
gap genes regulate the expression of the ________, which are expressed with double segmented periodicity in ____ transverse stripes
pair rule genes
7
where do adult vertebrate segments come from?
embryonic structures called somites
what does it mean to be a transient structure?
later stages - they disappear
three regions of somites - what are they
sclerotome (vertebrae and ribs)
myotome (skeletal muscles- apart from some facial muscles)
dermotome (demis of back)
what is the henson node in the chick involved in?
synchronizing gene expression across the emrbyo
what does the henson node have?
a population of somatic stem cells
FGF8 is a negative regulator. what does it do?
blocks somite formation
what does retinoic acid do in terms of somite formation?
it is positive
what is the determination front? / wavefront?
gradient of the two opposing signals
FGF and RA
can RA inhibit the effect of FGF8 on somite formation?
yes
somites can only form where there is not enough _____ to stop them from doing so
FGF8
n-cadherin causes cells to
stick to one another
eph/ephrin causes cells to
repel one another
_______ controls physical formation of somites
balance between attraction and repulsion
tissue will separate where ____ expressing cells meet _____ expressing cells
Eph
Ephrin
notochord is an ______ which provides _____
elastic rod
support
the henson node in the chick has a population of ___________ which have the ability to self renew to leave the node and generate ________
somatic stem cells
presomatic mesoderms
in vertebrates, segments bud off ________
one by one
in drosophila, segments all emerge at the __________ by ______ of existing space
same time
subdivision
somites for at a ______ from the node, and the presomitic mesoderm maintains a ______ length
given distance
constant
what are the three features of somite formation?
temporal
spatial
physical
so far, only genes related to ____ have been found operating in both simute formation and drosophila segmentation
hairy
changes in hairy expression match a ___ minute rhythm
90
Notch ____ hairy, hairy _____ notch
activates
inhibits
a stable equilibrium between notch and hairy is ________. the system _____
not reached
oscillates
does notch cycle? how is it expressed?
no
it is expressed constantly
notch signalling is important for ___ formation
somite
the stage of gene expression of these notch signalling components decide ___ a somite can form
when
FGF8 is a ______ regulator, which _____ somite formation
negative
blocks
FGs bind ________ receptors, and stimulate signalling in the ____ cell
transmembrane
recipient
blocking FGF8 function shifts the _____ where the somites form
position
retenoic acid is _____ on somite formation
positive
‘the determination front’ is what?
the two opposing signals or the ‘wavefront’
FGF8 forms a _______ gradient from the node, whereas RA formes a ________ gradient
posterior high
anterior high
FGF8 ______ somite formation, and RA can _____ this effect of FGF8
inhibit
inhibit
somites can only form where there is not enough ____ to stop them doing so
FGF8
human axioloids capture ________ of the segmentation clock
oscillatory dynamics
N-cadherin causes cells to _____
stick to one another
Eph/Ephrin causes cells to ______
repel one another
balance between attraction and repulsion controls __________ of somites
physical formation
tissue will separate where ______ expressing cells meet ______ expressing cells
Eph
Ephrin
