AP BIOLOGY

Detailed explanation-1: -The contractile ring shrinks at the equator of the cell, pinching the plasma membrane inward, and forming what is called a cleavage furrow. Eventually, the contractile ring shrinks to the point that there are two separate cells each bound by its own plasma membrane.

Detailed explanation-2: -During cytokinesis, the cleavage furrow appears suddenly on the surface of the cell and deepens rapidly (Figure 18-30). Because the cytoplasm is clear, the spindle can be observed in real time through a microscope.

Detailed explanation-3: -The DNA must be copied so there is a full set of DNA to pass on to each daughter cell.

Detailed explanation-4: -In an animal cell, a contractile ring of cytoskeletal fibers forms at the middle of the cell and contracts inward, producing an indentation called the cleavage furrow. Eventually, the contractile ring pinches the mother cell in two, producing two daughter cells.

Detailed explanation-5: -Cytokinesis is the physical process that finally splits the parent cell into two identical daughter cells. During cytokinesis, the cell membrane pinches in at the cell equator, forming a cleft called the cleavage furrow.