Lecture 6: Cleavage I Flashcards Preview

COB Embryology > Lecture 6: Cleavage I > Flashcards

Flashcards in Lecture 6: Cleavage I Deck (15):
1

Compaction

Outer blastomeres adhere via gap junctions and appear to lose their individual identity; E-cadherins, CAMs involved

2

What is the mechanism behind blastocoel formation?

Water transported into ball of cells due to Na+/K+ transporters around 4 days after fertilization

3

At one point is an embryo referred to as a blastocyst?

At the 58 cell stage

4

What are the components of the blastocyst?

Blastocoel, trophoblast, inner cell mass

5

What structures does the trophoblast give rise to?

Extraembryonic structures including placenta

6

What structures does the inner cell mass give rise to?

Embryo proper, other embryonic structures such as yolk sac and amnion

7

What is the difference in genetic control between non-mammals and mammals

In non-mammals: most early control of cleavage is through maternal genome until after blastulation; mammals: embryonic genome by 4 cell stage

8

Methylation

Inactivates genes by addition of methyl groups to specific regions of DNA molecules; can cause imprinting

9

Inside-Out Hypothesis

Fate of blastomere is determined by its position within the embryo, not from intrinsic properties

10

Cell Polarity Model

Fate of blastomere depends on plane of cell division during cleavage

Cleavage plane parallel: outer daughter cell becomes trophoblast, inner becomes inner cell mass

Cleavage plane perpendicular: both daughter cells become trophoblast cells

11

Which of the following genes is required to permit cleavage to proceed to 2-cell stage?

A. Cdx-2
B. Oct-4
C. Nanog
D. Sox2

B. Oct-4

12

Cdx-2

Gene essential for trophoblast cell differentiation, antagonistic toward Oct-4

13

Oct-4

Expressed in developing oocyte/zygote, required to permit cleavage to proceed to 2-cell stage, expressed in all morula cells, maintenance of undifferentiated state

14

Nanog

Produced by inner cells in later morula stage, maintains integrity of ICM with Oct-4; without Nanog inner cells differentiate into endoderm, wihtout Oct-4 inner cells differentiate into trophoblast

15

Sox2

First expressed in 8-cell stage, controls regulation of genes involved in differentiation