Flashcards in Lecture 6: Cleavage I Deck (15):
Outer blastomeres adhere via gap junctions and appear to lose their individual identity; E-cadherins, CAMs involved
What is the mechanism behind blastocoel formation?
Water transported into ball of cells due to Na+/K+ transporters around 4 days after fertilization
At one point is an embryo referred to as a blastocyst?
At the 58 cell stage
What are the components of the blastocyst?
Blastocoel, trophoblast, inner cell mass
What structures does the trophoblast give rise to?
Extraembryonic structures including placenta
What structures does the inner cell mass give rise to?
Embryo proper, other embryonic structures such as yolk sac and amnion
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
Inactivates genes by addition of methyl groups to specific regions of DNA molecules; can cause imprinting
Fate of blastomere is determined by its position within the embryo, not from intrinsic properties
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
Which of the following genes is required to permit cleavage to proceed to 2-cell stage?
Gene essential for trophoblast cell differentiation, antagonistic toward 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
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