BIOL 303 Lecture Notes - Lecture 3: Primitive Streak, Blastoderm, Sea Urchin

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browncheetah450

16 Oct 2011

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A-p and d-v axes are specified during oogenesis (before fertilization). The two types of blastoderms are synctial blastoderm and cellular blastoderm. Synctial blastoderm is when the nuclei share common (the same) cytoplasm after the 9th division. Cellular blastoderm is formed after the 13th division, when the cell membrane grows inwards of the plasma membrane and the nuclei get separate which forms the cellular blastoderm: define germ band (in respect to germ layers and function). The germ band elongates to posterior end of the embryo with the pole cells that come to the dorsal side of the egg (posterior dorsal side). The initial repeating patterning (parasegments) appear at the extended germ band. Genes that are involved in the determination of the anterior-posterior axis are two sets of maternal genes. (1) bicoid and hunchback regulate the anterior structure. (2) nanos and caudal regulate the posterior structures. These genes then regulate the zygotic gap genes, where are expressed in a overlapping layer.

Related Questions

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.

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

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.

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

In humans, the secondary oocyte forms:

at ovulation.
during telophase I.
after fertilization.
at birth.
all of the above.

In Ascaris:

The secondary oocyte is fertilized.
Two polar bodies are visible when the secondary oocyte is inprophase II.
Both a haploid and a diploid nucleus are present in a primaryoocyte during early prophase I.
Cell plates are formed during both anaphase I and anaphaseII.
No correct answer is given.

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

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

The spermatogonium is ________ , and the primary spermatocyteis __________ .

a. diploid,haploid b. haploid, diploid

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

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

a. Blastoderm. b. Archenteron.

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

purplegnat545

You are a scientist in a lab that studies how cell fates are specified during development. In particular, you are curious about muscle development. Muscle cells are derived from the mesoderm (one of the three primary germ layers) and are specified rather early in development. You are using the fruit fly, Drosophila melanogaster, as a model system to study the phenomenon of muscle fate specification. You have isolated a line of mutant flies you have named âwhimpyâ (wpy). The wpy phenotype appears to be inherited in a mendelian manner and acts as a recessive lethal, that is, Â¼ embryos from matings between two âcarrierâ flies die early in development. Analysis of the embryos suggests that muscle cells are not made. This suggests that the wildtype (normal) form of the wpy gene is required (necessary) for normal muscle specification during development.

- How would you test the hypothesis that wpy is sufficient to specify muscle cell fate? Explain your answer.

-Suppose wpy encodes a transcription factor. Describe one approach for determining the gene targets of the wpy protein.

1. In describing the timing of Drosophila development, researchers use AEL to mean âAfter egg layingâ, for example, 40 h AEL means 40 hours after egg laying. At 25o C, a fruit fly of 75 h AEL is at:

A. Embryonic stage

B. Larval stage

C. Pupal stage

2.The Green Fluorescent Protein (GFP) gene:

A. Is an endogenous gene that naturally existing in the Drosophila genome

B. Often exists as a transgene in the Drosophila genome, flies that bear a GFP gene is considered as transgenic flies

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BIOL 303 Lecture Notes - Lecture 3: Primitive Streak, Blastoderm, Sea Urchin

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