After fertilization, the zygote grows through a series of cell divisions called cleavage. The embryo does not grow in size although the cell number is increasing. How does this happen?
What will be an ideal response?
Meiosis of female germ cells involves unequal cytoplasmic divisions. After each meiotic division, one cell gets the bulk of the cytoplasm. As a result, meiosis of a female germ cell yields a single egg, with a large amount of cytoplasm. This egg becomes the zygote after fertilization. Cleavage carves up a zygote by repeated mitotic cell divisions. During cleavage, the number of cells increases, but the zygote's original volume remains unchanged. As a result, cells become more numerous but smaller in size.
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What will be an ideal response?