slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
CLEAVAGE PowerPoint Presentation
Download Presentation
CLEAVAGE

Loading in 2 Seconds...

play fullscreen
1 / 19

CLEAVAGE - PowerPoint PPT Presentation


  • 355 Views
  • Uploaded on

CLEAVAGE. 1. Ciona intestinalis. http://www.mun.ca/biology/scarr/Garstang_Hypothesis.htm. http://biodev.obs-vlfr.fr/recherche/biomarcell/ascidies/Anim-fromegg.htm. 2. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=.07EmbIt9ELpT-YFA1rDieIO4AMQFlmlIwWj.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'CLEAVAGE' - Jimmy


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide2

Ciona intestinalis

http://www.mun.ca/biology/scarr/Garstang_Hypothesis.htm

http://biodev.obs-vlfr.fr/recherche/biomarcell/ascidies/Anim-fromegg.htm

2

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=.07EmbIt9ELpT-YFA1rDieIO4AMQFlmlIwWj

slide4

E. G. Conklin, 1905 - In Styela partida, cells that contain yellow crescent pigment form muscle (mesoderm)

http://sdb.bio.purdue.edu/AboutThisSite/conklin.article.html

Swalla & Jeffery, 1995 - showed that a maternally derived mRNA was segregated into cells containing yellow crescent pigment.

4

slide5

Clear cytoplasm = ectoderm

Yellow cytoplasm = mesoderm

Dark gray cytoplasm = endoderm

Light gray cytoplasm = neural tube and notochord.

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=.0f0icUJoQpTbPzZ-do7pAF-n3I2E18sYrYZ

5

slide7

L

Ant

Point of sperm fusion with egg determines:

Dor

R

  • Position of grey crescent
  • Major axes of embryo
  • Position of dorsal lip
  • Position of first cleavage furrow

Ven

Pos

Wilhelm Roux, 1885

Second polar body 15-30 min after fertilization

Frog

5-10 min after fertilization

Pronuclei will fuse 1.5 - 2 hr after fertilization

7

http://www.md.huji.ac.il/~yisraeli/embryology/embryo.html

slide8

What do these experiments tell us?

  • In some species, the cytoplasm of the zygote is very organized.
  • That maternally derived cytoplasmic information is sequestered into specific cytoplasmic compartments.
  • The end result - maternal mRNAs end up in specific groups of cells - determines those cells eventual fate
  • the cells containing the yellow pigment cytoplasm of Stylea’s embryos form muscle
  • the cells of the frog embryo that contain gray crescent cytoplasm become the chordamesoderm and eventually the notochord.

8

slide9

Purposes of cleavage

  • Decrease cell size
  • Increase cell number - allows for formation of blastocoel in many species by a process called cavitation.
  • In some cases, distribution of maternal cytoplasmic information to specific groups of cells
  • Beginning of Differentiation - as cleavage proceeds, you reach a point where the blastomeres are no longer totipotent
  • Synthesis of embryo derived mRNA for direction of future development begins during cleavage. Mammals - starts after a few cleavage divisions; Frogs - starts during late blastula stage

9

slide11

V

IV

III

II

I

STARFISH CLEAVAGE - EQUAL HOLOBLASTIC

I

A

~32 cell stage

A

Meiosis complete at ovulation

Isolecithal, oligolecithal, microlecithal egg

Sagittal view

V

View of animal pole

View of vegetal pole

V

11

slide12

V

IV

III

I

UNEQUAL HOLOBLASTIC (may be meroblastic cleavage, but not always)

Amphibians - meroblastic,unequal starting with 3rd cleavage division

32 cell stage

4 cell stage

8 cell stage

II

I

2 cell stage

16 cell stage

A

Sagittal view

View of animal pole

View of vegetal pole

Ovulated as primary oocyte. First meiotic division completed in oviduct, second after fertilization.

A

V

Mesolecithal vs telolecithal

Frog blastula

18 hr

1st - 3.5 hr

2nd - 4.5 hr

3rd - 5.5 hr

V

http://www.luc.edu/depts/biology/dev/stages.htm

http://www.its.caltech.edu/~bi12/2003/movies/xclvgtop.mov

12

slide13

Blastodisc

Structure of the chicken (bird) shelled egg

Polylecithal or megalecithal egg (huge amount of yolk)

13

slide14

I

II

III

IV

V

I

AVIAN CLEAVAGE - DISCOIDAL

Ovulated as primary oocyte.

Meiosis I completed almost immediately after ovulation.

Meiosis 2 completed after fertilization.

1st - 3 hr

2nd - 3.5 hr

3rd - 4 hr

4th - 4.5 hr

5th - 5 hr

Looking down on the animal pole.

Yolk

A

Discoidal cleavage is a type of meroblastic cleavage

Yolk

14

slide15

A

15

slide16

Delamination

Movie of delamination in digital lab manual

Polyinvagination

16

slide17

SUPERFICIAL CLEAVAGE - INSECTS

Superficial cleavage is a type of meroblastic cleavage

pole plasm

17

http://www.luc.edu/depts/biology/dev/insect.htm

slide19

Human embryo cleavage and cavitation.

19

http://www.erin.utoronto.ca/~w3bio380/lecture/Lect11/L11.htm