Exercise 3 - Cleavage

Question 1

Cleavage:

During cleavage, the ____ divides by mitosis into two daughter cells called ___ that leads to a four-cell embryo

It continues until they get a multicellular ____ embryo. Early embryonic cells usually enter mitosis faster than typical adult ____ because the embryonic cell cycle has short or nonexistent G1 and G2 phases.

Answer 1

zygote
blastomere

blastula
somatic cells

Question 2

Cleavage:

Little yolk is found in the ____ which divides into two equal size cells _____

In contrast, the fertilized _____ cleaves incompletely (_____)

Answer 2

isolecithal human oocyte
holoblastic cleavage

telolecithal chicken oocyte
meroblastic cleavage

Question 3

Cleavage:
The furrow forms up to fifty times faster at the ___ than the yolk-laden ____

Answer 3

animal pole

vegetal pole

Question 4

Types of cleavage:
___ through animal-vegetal axis

____ parallel to the animal-vegetal axis but not through the poles

____ through the cell’s equator perpendicular to the animal-vegetal axis

___ perpendicular to the animal-vegetal axis but not htrough the cell’s equator

Answer 4

meirdional

longitudinal

equatorial

latitudinal

Question 5

Cleavage pattern:

____ cleavage furrow completely separates both daughter cells

____ Cleavage is incomplete; daughter cells remain connected. After many cleavages, the embryo is a cluster of cells (blastoderm) located on top of a mass of yolk.

____ two equal-sized daughter cells result due to a central positioning of the mitotic spindle

____ one large and one small daughter cell are produced due to mitotic spindle placement at one side of the embryo

____cleavage plane is perpendiular or parallel to the previous one

____ cleavage plane busects zygote into right and left haves. Subsequent cleavages result in an embryo with two halves that are mirror images of each other

____ first cleavage is meridional: during second cleavage one blastoemre divides meridionally, and the other equatorially.

____ cleavage is restricted to the blastodisc of the telolecithal oocyte.

____ cleavage is restricted to a rim of cytoplasm in the centrolecithal oocyte

Answer 5

Holoblastic

Meroblastic

Equal

Unequal

Radial

Spiral

Bilateral

Rotational

Discoidal

Superficial

Question 6

Sea Urchin cleavage:

The small amount of yolk allows the ____ to penetrate through the cytoplasm rapidly

Answer 6

ccleavage furrow

Question 7

Sea Urchin cleavage:

Cleavages occur at ____ intervals but the first cell cycle lasts ____

Cytokinesis takes ____

Answer 7

30 minute intervals
one to 2 hours

10 minutes