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BIOL 303 Lecture Notes - Lecture 4: Regional Differentiation, Primitive Streak, Hypoblast

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browncheetah450
16 Oct 2011
School
McGill University
Department
Biology (Sci)
Course
BIOL 303
Professor
Dragana Miskovic

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Document Summary

Birds have telolethical yolk, which is there is a large amount of yolk towards one pole of the egg and very less cytoplasm, which is known as blastodisc. Cleavage occurs on the side with the very little cytoplasm on top of the yolk. The primitive streak is the accumulation of cells in the middle layer between the epiblast and the hypoblast. The epiblast also thickens at the posterior end. The primitive groove is when the cells converge and depression occurs, which forms an opening allowing cells to pass to the blastocoels. The first cells to pass through the primitive streak are the endodermal precursors: compare and contrast formation of nieuwkoop center in amphibians and birds. Explain your reasoning (in respect to their role in gastrulation). The posterior marginal zone (bird) is similar to the nieuwkoop centre (amphibian), the. Nieuwkoop centre are the dorsal most vegetal cells of the blastula that induce organizer cells (dorsal lip).

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Related Questions

The infolding of the Xenopus dorsal blastopore lip, regression of Hensen's node in chickens, and the formation of the hypoblast in Zebrafish by the embryonic shield all use which mode of gastrulation?

Involution
Invagination
Epiboly
Ingression
Delamination

pleas pleas do all parts

1-Are both the egg and zygote of a sea star the same size?

2-Do the cells of a two-cell sea star embryo differ in size?

3-Does the sea star embryo appear to be growing during cleavage?

4-What structures will the archenteron develop into?

5-What obvious visual change occurs in a frog egg upon fertilization?

6-How is the orientation of the blastocoel in an amphibian blastula different than that of a sea star?

7-What structures will form from the neural fold of the frog embryo?

8-In a chick embryo at gastrulation, what does the primitive streak indicate?

9-What are the segmented units that are visible along the dorsal axis of the 33 hour chick embryo?

10-The basic stages of development are quite similar for a wide range of organisms. How would you explain such consistency?

  1. An organism with extensive yolk, such as the chick,

A) has incompletecleavage. D)forms a blastoderm but no blastocoel.

B) has yolk evenly distributed in the egg. E) has completecleavage.

C) fails to synthesize DNA duringcleavage.

  1. Invagination

A) occurs in sea urchins.

B) forms the archenteron in echinoderms.

C) creates unique positions for new cell interactions.

D) requires unique cell movement.

E) All of the above

  1. When the blastopore dorsal lip is grafted from one frog embryoonto a second embryo, the second dorsal lip will

A) change the developmental fate of the surrounding cells.

B) change the polarity of the adjacent segments.

C) cause rapid cell division.

D) block gastrulation.

E) change the prospective potency of the surrounding cells.

  1. Gastrulation in birds differs in many ways from gastrulation infrogs. The main feature that both have in common is that

A) the neural tube forms.

B) somites are created.

C) cells from the surface of the blastocyst migrate to form thegut.

D) three germ layers are established.

E) All of the above

  1. In humans, the secondary oocyte forms:
  1. at ovulation.
  2. during telophase I.
  3. after fertilization.
  4. at birth.
  5. all of the above.

  1. In Ascaris:
  1. The secondary oocyte is fertilized.
  2. Two polar bodies are visible when the secondary oocyte is inprophase II.
  3. Both a haploid and a diploid nucleus are present in a primaryoocyte during early prophase I.
  4. Cell plates are formed during both anaphase I and anaphaseII.
  5. No correct answer is given.
  1. A gastrula is:

a. an embryo that is younger than a blastula.

b. a stage in development that has three tissue layers.

c. a type of egg that has yolk concentrated at one end of thecell.

d. an opening in the center of an early embryo.

e. something else

  1. A human cell containing 22 autosomes and one Y chromosome isa

a. somatic cell of amale b. zygote

c. somatic cell of afemale d. a sperm e. an ovum

  1. The spermatogonium is ________ , and the primary spermatocyteis __________ .

a. diploid,haploid b. haploid, diploid

c. haploid,haploid d. diploid,diploid e. triploid, diploid

  1. The first cavity formed in the rapidly dividing starfish embryois the:

a. Blastoderm. b. Archenteron.

c. Neural groove. d. Blastocoel. e. Trophoblast.