05 cleavage
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8/9/2019 05 Cleavage
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CLEAVAGE
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http://biodev.obs-vlfr.fr/recherche/biomarcell/ascidies/Anim-fromegg.htm
Ciona intestinalis
http://www.mun.ca/biology/scarr/Garstang_Hypothesis.htm
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid.!"#mb$t%#&p'-()A*r+ie$,A)lml$w01
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#. G. 3onklin4 *%!5 - $n 6tyela partida4 cells that contain yellow crescent pigment form
muscle 7mesoderm8
http://sdb.bio.purdue.edu/About'his6ite/conklin.article.html
6walla 9 effery4 *%%5 - showed that a maternally derived m;<A was segregated into
cells containing yellow crescent pigment.
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3lear cytoplasm ectoderm
(ellow cytoplasm mesoderm
+ark gray cytoplasm endoderm
&ight gray cytoplasm neural tube and notochord.
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid.!f!ic=op'b>@-do"pA)-n$B#*Cs(r(@
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)rog
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7http://www.md.hu1i.ac.il/Dyisraeli/embryology/embryo.html
)rog
5-*! min after
fertiliation
6econd polar body
*5-! min after
fertiliation
>ronuclei will fuse
*.5 - B hr after
fertiliation
>oint of sperm fusion
with egg determines:
*. >osition of grey crescent
B. a1or aEes of embryo
. >osition of dorsal lip
. >osition of first cleavage
furrow
Wilhelm Roux,
1885
L R
Ant
Pos
Dor
Ven
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*. $n some species4 the cytoplasm of the ygote is very
organied.
B. 'hat maternally derived cytoplasmic information is
seFuestered into specific cytoplasmic compartments.
. 'he end result - maternal m;<As end up in specific
groups of cells - determines those cells eventual fate
a. the cells containing the yellow pigment
cytoplasm of 6tyleas embryos form muscle
b. the cells of the frog embryo that contain gray
crescent cytoplasm become the
chordamesoderm and eventually the
notochord.
0hat do these eEperiments tell us?
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*. +ecrease cell sie
B. $ncrease cell number - allows for formation of blastocoel in many
species by a process called cavitation.
. $n some cases4 distribution of maternal
cytoplasmic information to specific groups of cells
. eginning of +ifferentiation - as cleavage
proceeds4 you reach a point where the
blastomeres are no longer totipotent
5. 6ynthesis of embryo derived m;<A for direction offuture development begins during cleavage.
ammals - starts after a few cleavage divisionsI
)rogs - starts during late blastula stage
>urposes of cleavage
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0
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A
V
A
V
Sagittal view
View of animal pole
View of vegetal pole
STARFISH CLEAVAGE - EQUAL HOLOBLASTIC
IIIIIIIIVV
DB cell stage
eiosis complete at ovulation $solecithal4 oligolecithal4 microlecithal egg
=<#=A& H,&,&A6'$3 7may be meroblastic cleavage but not always8
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*st - .5 hr
Bnd - .5 hr
rd - 5.5 hr
A
Sagittal view
View of animal pole
View of vegetal pole
=<#=A& H,&,&A6'$3 7may be meroblastic cleavage4 but not always8
Amphibians - meroblastic4 uneFual starting with rd cleavage division
V
II
2 cell stage4 cell stage
IIIII
8 cell stage
IV
16 cell stage
V
32 cell stage
http://www.luc.edu/depts/biology/dev/stages.htm
http://www.its.caltech.edu/Dbi*B/B!!/movies/Eclvgtop.mov
,vulated as primary oocyte. )irst
meiotic division completed in
oviduct4 second after fertiliation.
esolecithal vs telolecithal)rog blastula
*C hr
A
J
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6tructure of the chicken 7bird8 shelled egg
>olylecithal or megalecithal egg 7huge amount of yolk8
Blastodisc
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AVIAN CLEAVAGE - DISCOIDAL
IIIIIIIIVV
Yolk
Yolk
&ooking down on the animal
pole.
+iscoidal
cleavage is a
type of
meroblastic
cleavage
,vulated as primary oocyte.
eiosis $ completed almost
immediately after ovulation.
eiosis B completed after
fertiliation.
*st - hr
Bnd - .5 hr
rd - hr
th - .5 hr
5th - 5 hr
A
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A
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>olyinvagination
+elamination
Movie of delamination in digital lab manual
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SUPERFICIAL CLEAVAGE - INSECTS
pole plasm http://www.luc.edu/depts/biology/dev/insect.htm
6uperficial cleavage is a type of
meroblastic cleavage
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19http://www erin utoronto ca/~w3bio380/lecture/Lect11/L11 htm
Human embryo cleavage and cavitation.
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