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

Answer: (E)

Verified step by step guidance

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.