Which statement about cleavage in placental mammals is true?
A) As in other animals, the loose ball of cells at the 8-cell stage of mammals becomes asymmetrical when cells form tight junctions and increase contact with one another.
B) Unlike cleavage in sea urchins and frogs, gene products expressed by blastomeres affect cleavage in mammals.
C) As in sea urchins and frogs, the number of cells in the embryo increases in a regular progression from 1 to 2 to 4 to 8 to 16 to 32, and so on.
D) In the second division, cleavage divides the blastomeres in a plane that is perpendicular to the animal-vegetal axis.
E) At the end of cleavage, the embryo is called a blastocyst because it lacks a blastocoel.

Question

Quizplus · Accepted Answer

In placental mammals, unlike sea urchins and frogs, gene expression in blastomeres affects cleavage. This is because transcription is initiated at the 4-cell stage, and each blastomere expresses different genes, leading to cell differentiation.

Which Statement About Cleavage in Placental Mammals Is True