Multiple Choice
As an animal develops, organs form and the body transforms into a shape typical of the species in a process called __________.
20. Development
Animal Development
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Up to the eight-cell stage, the blastomeres of a mouse embryo can each form a complete embryo if isolated. This indicates that __________.
A
differentiation does not depend on cytoplasmic determinants
B
the mouse embryo is strongly polarized
C
cytoplasmic determinants are unevenly distributed during the early cleavage divisions
D
mammalian embryos do not experience the progressive restriction of potency characteristic of other embryos
E
cells of mammalian embryos remain totipotent until at least the eight-cell stage
Verified step by step guidance1
Understand the concept of totipotency: Totipotency refers to the ability of a single cell to divide and produce all of the differentiated cells in an organism, including extraembryonic tissues. In the context of early embryonic development, totipotent cells can give rise to a complete organism.
Recognize the significance of the eight-cell stage: In many mammals, including mice, the cells of the embryo up to the eight-cell stage are considered totipotent. This means that each cell has the potential to develop into a complete embryo if isolated.
Analyze the options given: The problem provides several statements about the nature of early embryonic development. We need to determine which statement is supported by the fact that each blastomere can form a complete embryo if isolated.
Evaluate the role of cytoplasmic determinants: Cytoplasmic determinants are molecules within the egg cytoplasm that influence the fate of cells. If differentiation depended heavily on these determinants, isolated cells might not be able to form a complete embryo. The ability of each blastomere to form a complete embryo suggests that differentiation is not solely dependent on these determinants at this stage.
Conclude with the correct interpretation: The ability of each blastomere to form a complete embryo indicates that mammalian embryos, like those of mice, do not experience the progressive restriction of potency characteristic of other embryos until after the eight-cell stage. This means that the cells remain totipotent until at least this stage.
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