| Because of the enormouns amount of yolk, not a single cleavage furrow is able to penetrate through the yolk, and divide the egg completely. |
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| The process begins during chromosome segregation, when the ingressing cleavage furrow begins to partition the cytoplasm between the nascent daughter cells. |
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| Spindle asymmetry would provide a plausible mechanism for the positioning of the cleavage furrow, which could explain the observed sibling cell size asymmetry. |
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| In one such experiment, a glass bead on the end of a needle was inserted into a fertilized sand-dollar egg so that it interrupted the first cleavage furrow. |
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| At 38 minutes after insemination, the first cleavage was observed and the first cleavage furrow of the blastodisk appeared at 53 minutes. |
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| However, in cells that formed a cleavage furrow, the furrow positions were not altered. |
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| Constriction of this ring pulls the plasma membrane into the cell interior during cleavage furrow ingression. |
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| The spindle midzone was compressed by the ingressing cleavage furrow. |
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