[Campbell Biology P.431] Which of the following statements correctly describes the role and ... | Practice Question

Which of the following statements correctly describes the role and distribution of cytoplasmic determinants in early embryonic development, as depicted in Figure 18.17a and the accompanying text?

  • A: Cytoplasmic determinants are evenly distributed throughout the unfertilized egg, ensuring all daughter cells receive the same developmental signals.
  • B: After fertilization and mitotic divisions, different embryonic cells are exposed to varying combinations of cytoplasmic determinants, leading to differential gene expression.
  • C: Cytoplasmic determinants are primarily proteins synthesized by the zygote's own genes after fertilization.
  • D: The uneven distribution of cytoplasmic determinants primarily affects the physical shape (morphogenesis) of the embryo, not gene expression.

Explanation

The text states that 'Maternal substances in the egg... called cytoplasmic determinants Figure 18.17a ... are unevenly distributed in the egg. After fertilization and mitotic division, the cell nuclei of the embryo are exposed to different combinations of cytoplasmic determinants and, as a result, express different genes.' This directly supports option B.