non mammal cleavage
synchronous division no growth no transcription no g1 and g2 dependent on mothers mRNA
mammal cleavage
slower not synchronous plane of cleavage can differ between cells in same cycle trnascription still occuring undergo compaction (e cadherin)
What is string protien in drosophila homologue of and how does it regulate CDK1
cdc25
cyclin b bind and activates CDK! and present G2 and mitosis
Wee1 phosphorylates tyr 15 on CDK1 - inact during Gā
CDK1 phosphy again by AK
CDK1 activated when 1st phosphate on tyr removed
cdc25(string) removes phosphate on CDK1
what does activated CDK1 do
activate histone 1 -chromosome condensation
activate MAP - spindle formation
inactivate lamin - nuclear envelope breakdown
non mammals cell div after cleavage
non synchronous
occurs only in specific regions for tissues
G1 and G2
dependent on zygotic transcription
potency definition
range of cell fates a cell line can become
differentiation defn
process cell dopt final shape
comminted deifnition
will become fate under normal env conditions but change in conditions will results in new cell fat
determination
irreversible commitment of a cell to a particular fate
p granules in C elegans an eg of
segregation of cytoplasmic determinants
mutant phenotype of par1
mex5-6
no Pie1 localisation none in either d cell
in both cells (no degradation)
mutant pie1
no gonads
sperm entry at
par3/par6/aPKC distribution
Par1/Par2
Mex 5 where and role
posterior
anterior (tensile network contratct ant)
posterior (fill gap)
anterior degrade pie1
volvox example of
asymmetric division and cell fate
how is gonida cell in volvox formed
6th cell in anterior asymmetric - gonidal cell is big
genes important in volvox gonida
gonidaless - imp in asym div plane
regenerator a - transcriptional repressor in somatic cell
late gonida - tran repressor in gonida - turn off somatic cell pr
pharynx eg of
cell cell signalling giving fate
WT fate of Aba
pharynx skinn neurones
when p1 removed what happens
Aba on pharnygeal abp no muscle
EMS removeed
Aba no pharyngeal
therefore EMS give signal for ABa pharyngeal cell
P2 ablated
Abp make pharyngeal too (norm doesnt)
therefore p2 give signal make abp deaf to EMS signal
change position EMS and P2
when P2 in contact with ABa doesnt make p cell
what is APx1
signal on P2 membrane
GLP1 is
receptor on ABa and ABp membrane
evidence of lateral inhibiton in dros bristle
ablate cell which become bristle - neighbour take job
repeat see size of group
what is the proneural cluster
cells which have been inhibited by sense organ precursor
non autonomous is
cell doesnt need therefore signal
autnomous
cell requires therefore receptor
how is notch activated by delta
delta binds
notch intracellular domain cleaved
notch mutant in bristle scneario
all develop as sense organ precursor as no lat inh rec
delta mutant in bristle
bristle in middle as periphery cells get signal from other clusters
what are the proneural genes that set up proneural cluster
achetate scute
how do delta/notch causes lat inh
activate coactivator Su(H) which activates E(Spi) a repressor, inhibits of proneural genes achetate and scute.
what genes form complex to activate trichome development
GL1, TTG1, GL3 - turn on GL2
what in non functional complex of trichome development
Try, CPC form with TTG1 and GL3
how does trichome spacing form
GL1 and GL3 canāt diffuse
TTG1 can and so can Try and Cpc
try and cpc diffuse to neighbours and repress trichome dev
limited how far can diffuse = where next trichome forms.
what is a morphogen
a molecule that defines two or more cell fates at different concentrations
Vulva dev in C. elegans eg of
relay system (cell pass signal on)
role of anchor cell
give signal to become primary (P6p) or seconday (p5p/p7p) become vulva
ablate = no vulva
is lin 3 rec or signal
signal - acts as a morphogen
describe experiment show lin 3 is a morphogen
heat shock protein diff heats - diff amounts produced
no lin3- tertiary
little- secondary
lot -primary
role of lin12
rec for lin 3, inv in its lateral inhibition on p5p/p7p - result in suppression of primary and induction of seconary cell fate
describe epiboly
shhet merge cells thinner and cover larger area
describe convergent extension
within sheet intercalate into thin line - imp in body axis
where is VG1 in oocyte
vegetal cortex
role of Vg1
drives animal/vegetal identity. (is a TGfbeta growth factor)
spermy entry at
ventral
what is cortical rotation
90 min after fertilisation 30degree turn of cortex
expose vegetal cortex to animal pole
forms Nieuwkoop centre
role of Nieuwkoop centre
set up D/V polarity in blastula/defines dorsal side
graft N.centre onto ventral
twinned embryo 2 dorsal sides
effect of lithium
dorsalised embryo
directly inhibits GSK3 (no b catenin degradation)
B catenin role
nuclear TF after c rot on dorsal side move to nucleus activates TF which specify dorsal side when inject into ventral has dorsal effect
role GSK3 and disheveled
B catenin degradation
only ventral as dishevelled block dorsally
cortical rotation moves disheveled to dorsal side
role of spemann organizer
further pattern A/P, D/V and N syst induction
role of Vegt
activates mesoderm induction
organ of mesoderm
skeleton, muscle, kidney,blood.
why is interactionof animal and vegetal pole important
mesoderm induction
fate of dorsal mesonoto
notochord muscle
fate of ventral meso
blood vessel
1st stage of mesoderm induction
signal from vegetal
give ventral mesoderm default
(vegt likely)
2nd stage mesoderm induction
Nieuwkoop centre indices spemann and notochord (b catenin)
3rd stage mesoderm induction
spemann organiser gives signal modify dorsal side of mesoderm (BMP antagonist)
4th stage of mesoderm induction
ventral pattering induction from ventral region (subdivide muscle,kidney, blood) (BMP)
what features of Vg1 make candidate of mesoderm inducer
active can induce dorsal mesoderm in isolated animal cap and ventralised embryos
at low conc induces ventral mesoderm
features of activin make mesoderm inducer candidate
has conc dependent action
high- notochord muscle
low - muscle
VegT - why possible mesoderm inducer
when decreased no mesoderm
describe role of noggin
is a dorsalising signal from organizer
BMP antagonist
chordin similar role
BMP
bone morphogenetic protein
low at organizer high at ventral
give ventral signal/identity
3 stages of gasstrulation
primary mesenchyme transition
invagination of endoderm
archeteron form
3 stages of xenopus gastrulation
involution - rolling in of endoderm and mesoderm at blastospore
convergent extension of mesoder
epiboly - spreading of ectoderm as endoderm and mesoderm move in
situs solitus is
normal
situs inversus is
reversal of axis
right isomerism
all body organ develop as if on right
left isomerism
all body organ develop as if on left
how was it found cili involve in L-R axis
inversus viscerum mut in mouse -random placement of internal organ (mut in pr which code for dynein)
situs inversus - reversal of handedness (mut in pr inversin part of cilia)
when no flow at cilia node phenotype is
right isomerism
disorganised flow at cilia node ptype is
left isomerism
opposite direction of flow at cili node ptype is
situs inversus
how is nodal affected bu cilia flow
nodal asym distributed by cilia
act Pitx2
lefty - anatgonist of nodal in LHS of embryo
no cilia no gene asym
how is L/R axis established in echinoderm
nodal expr on RIGHT
larva rudiment on left - become adult organ
remove nodal - 2 rudiment
snail L/R axis formed
sinistral - L rot
rostral - R rot
hve equivalent of nodal and pitx2
R twist nodal on R hs
what is hensons node
in somitogenesis where cell proliferation occurs
constantly regress away from head
gives rise to tail
what is presomitic mesoder
unpatterned tissue
12 somites worth of cells
is a constant length of 12cm
how is somitogenesis different in chick to drosophila
somite bud off one by one
most anterior segment is the oldest
what are the three features of control of somitogenesis
temporal - constant time
spatial - constant length
physical - how cells bud off
how is hairy expressed in vertebrate somitogenesis
expressed in presomitic mesoderm and youngest somite
has inconsistent expression
as dynamic (shown fix two side of noto)
hairy expression matches 90 min rhythm, in a posterior to anterior wave
when a new somite about to form is conc in anterior
what makes notch dynamic
notch activates hairy hairy is a trans repressor auto represses itself as unstable hairy inh notch this creates an oscillation of act hairy
what makes somite form given distance from node
FGF8 gradient - made at node
when block fgf8 somite more posterior
FGF8 inh somite formation
where does somite form
where FGF8 gradient and hariy act collide
causes gene expression changes allow somite to form
what causes physical change in somitogenesis
N cadherin causes cells to stick Eph/ephrin cells repel one another balance - control physical properties in presomitic mesoderm layer of eph/ephrin expressing cells that do not break apart as N cadherin also expressed somite form wheno n cad
what is somitogenesis like in beetle
pair rule gene inv in circuit with less involvemnet form gap gene
somitogenesis in chelicerate
pair rule gene expressed in stripes that progress from p to a in the unpatterned growth zome
spider somitogenesis involves
hairy expression in pulsating fashion
what are somites?
segments of paraxial mesoderm
what are the 2 clusters of homeotic gene in drosophila
bithroax
antennapedia
how many clusters of hox gene in mammals and why?
four clusters with paralogs
why KO less extreme in
what do high levels of retinoic acid do when injected in utero
cause misexpression of hox genes
more posterior structures
where is retinoic acid concentration highest and why?
caudal end of hindbrain
as this where enzyme which makes is - retinaldehyde dehydrogenaseIII
what does an acitvated retioic acid recpetor have on it
has coactivator bound protein which bindss to receptor binding element to activate genes
differences between vertebrate and drosophila hox genes (4)
vert x100 more compact
shared regulatory elements in vert independent in dros
hox domains est gap/pair rule in dros vs ra and somitogenic clock in vert
vert have FGF8 grad
genetic causes of developmental defects
single gene disorder (FGFR3 and achondroplasia)
multigene disorder
age
inbreeding
eg of broad class developmental malformation
failure to seperate
failure to fuse
epigentic dev defect
beckwithh wiedemann syndrome - over grown tumours on kidney risk, slows by 8 yrs
due to epigen alterations on chr 11p15
what are teratogens
env agents which alter development but not by mutation
eg of teratogens
cyclopamine - produced by false helleborne easten by pregnant animal = cyclopic young
works by blocking Shh signal as binds and inhibit smo
Thalidomide bind cereblon, which forms complex imp in limb outgrowth and expression of FGF8 no thalidomide no fgf8
how does sonic hedgehog signalling work
Shh binds to patched and inhibits
patched inhibits smoothened
smooothened act Gli ~(TF) switch on genes
imp in pattering midline structures notochord and fllor plate of neural tube
what is basal cell carcinoma
most common cancer skin
aar of hyperact of shh pathway
cyclopamine pot treatment
why is cyclopamin pot treatment of meullblastoma
brain tumour
clocks shh
where are embryonic stem cells found
icm of blastocyst
where are adult stem cells found
hair follicle
crypts
bone marrow
what is transdifferentiation
stem cell from one organ given correct signal to contribute to another organ.
what is the cocktail of TF that make ips
OCT2/4,SOX2, KLF4 CMYC.
how long after fertilisation does segmentation occur in drosophila
8 hrs
how many parasegments in dros
14
bicoid lof ptype is
2 post ends
where is bicoid mrna localised
anterior
where is bicoid pr
in gradient as embryo a syncitium, highest at ant
ectopic expression of bicoid ptype
head
how does bicoid regulate target gene
bind promotor
hunchback mut have
head/thorax defect
role of nanos/ expression
in pos
repress hunchback
interaction between bicoid and caudal is
bicoid inh caudal translation
therfore in post
mut ptype of gap genes
consecutive segments
what are gap gene expression control by
maternal effect genes
gap gene cross reg themselves
what are pair rule gene control by
primary -gap gene and bicoid puts into 14 stripes of gene
secondary - reg by primary
role of pair rule gene even skipped
expr in odd paraseg
mut have no para seg
trnscriptional repressor
role of fushi tarazu
is a secondary pair rule gene
expr in even no paraseg
encode transcriptional act (complemenery function)
what is the antennapedia mut
GOF antenna into leg like appendages
what is probiscipedia mut
gof
proboscis into leg like structure
what are features of a hox gene
homeodomain
hexapeptide binding motif (diagnos hox id)
role of polycomb protein
remodel chromatin
lock in stable expression
gene off/silenced
role of trithorax protein
main action to maintain gene expression
keep chromatin open
bind dna and alter structure of chromatin
no polycomb and trithoraz protein mean
hox gene expression set up but not maintained
LOF mut in dros hox
next hox gene will fill/take on identity
GOF mut in dros hox
transform anterior to more posterior identity
when express two hox gene most posterior wins
desicrbe the bithorax complex in drosophila
3 genes
ubx - when del =wing in 3rd seg as T3 get T1/T2 identity
with antp expr as ubx norm repress antp
what is macroevolution
certain change cause big morpho change
what does ubx supress
leg formation
how does abdb reg yellow body
cis reg element
does brine shrimp ubx repress limb
no ehy thoracic limb
how is plant development differ from animal
post embryonic development
continuous growth as meristem
can change development programme according to environmental cues
cells can not move
anticlinal division
perpendicular to surface
periclinal division
parallel to surface
what role of gene angusfolia
control width of leaves
rotudilfolia 3 role
control length of leaves
what are the four parts of plant embryo
cotyledon
meristem
hypocotyl
root
what is the apical cell division programme
x2 anticlinal
1 periclinal
basal cell division programme
expand longitudinal
divide periclinal
wox gene role
determine cell div programme
where are wox2/wox8/wox9 expressed
wox2 apical by 16 cell only top wox8 suspensor wox9 suspensor 16 cell in bot embryo
wox2 mut affect
change 8-16 cell division from periclinal to anticlinal
no embryo made
wox8 9 mut
abnormal cell div in embryo and suspensor
ATMERISTEM LAYER1 expression/mutant ptype
in apical
after 16 only in l1 layer of epidermis thruout plant life
mutant lethal w no epidermis
what gene does CUC3 turn on
shootmeristemless (STM1) in late globular
role of STM1
shoot apical meristem identity
Plethora (PLT) gene role
root identity
plt is dose ddependent what does it specify at low/high
low - promote mitotic activation of stem cell daughter
high - promote stem cell identity and maintenance
at 1 cell stage where is auxin flow
suspensor to embryo
what PIN maintain auxin flow upto 8 cell stage
pin7/pin1
auxin flow from globular atage onwards is directed
into tip of cotyledon and root by pin1
where is auxin flow directed in heart stage
internally by pin 1
what is the mutant ptype of LEC1
hair on cotyledon
overexpress -embryo everywhere
rolfe of wuschel
only in SAM make initial cells
role of clavata
clavata in pathway which anatgonise wus to maintain cell proliferation
what genes are in the central zone
STM Wus
what genes are in peripheral zone
clavata
what are decussate leaves
at 90 degree
what are distichous leaves
180 degree
what are the hypothesis for leaf development
inhibitory field
biophysical
general control of genes
what is inh field hypo
position of pressent primordia important for next primorida
pre existing primordia inhibit new priordia
when isolate one the next one forms noramlly but one after forms closer w=to where removeed primordia shoud be
strongest at youngest
what is the biophysical hypothesis
uneven thickness
weaker area physical force = new leaf form
role of expansins
make cell wall weaker where they are present
loosen linkage between cellulos microfibrils
ectopic expr = new primordia
role of cytokinin
regulate size of stem cell niche
role of AHp6,
inhibits cytokinin and establishes pattern of signalling in meristem
what genes aare turned off when acquiring determinate leaf identity
KNOX1 and STM1 are merostem specific genes
what genes are turned on for determinate leaf identity
ARP genes promote determinate growth and differentiation
what are adaxial genes
HDZIP phb,rev,phv
what role does miR65 have in making phb only expressed in adaxial
cleaves transcript, therefore confing to one side as only expressed abaxial
abaxial genes
yabby
kandi
what does blade devlopemtn require
ab/ad boundary
role of CUC
seperates cotyledon
role of CUC2
growth repressor
when continously expressed no serration
interaction of auxin and cuc2
auxin repress cuc2
role of speechless in guard cell development
asym entry div
role of mute in guard cell development
control cell fate (smallest become guard cell)
FAMA role in guard celll development
symm exit division
role of EPF2 in guard cell development
role in spacing
ligand produced in stomata diffuses inhibits neighbours from becoming guard cell
over expr = no guard cell
what activates Flowering locus T (FT)
constants
what is constants controllled by
circadian rhythm
degraded at dark therefore peak at end of day
constants bind FT promoter and act transcription
what is FD
TF FT bind to
together activate AP1 which is sufficient for floral induction
what is leafy
master gene for floral id is a TF
what antagonises leafy expression
TFL1
example of a b c genes
a - apetala 1,2
b- apetala 3 pistilata
c - agamous
agamous mu
indeterminate meristem
cycloidea mut
no dorsal petal all ventral
radialus mut
all ventral petal
divaricata mut
show lateral default