Open Response Scoring Guide

Correct answer:

A muscle cell during interphase would be responsible for contraction to aid a muscle in movement.  The muscle cell could grow and carry out protein synthesis during this time.  Replication of the cell’s DNA would occur towards the end of interphase.

After interphase, cell division would begin.  First mitosis, the division of the nucleus, would occur.  Mitosis begins with telophase.  During telophase, the nuclear membrane disappears, chromosomes become visible, and spindle fibers begin forming.

Metaphase begins when the chromosomes line up along the equators of the cell.  Spindle fibers attach to the chromosomes.  During anaphase, the spindle fibers begin to pull the chromatids apart.

Finally during telophase, the chromosomes reach the poles of the cell.  Nuclear membranes surround the two groups of chromosomes.  Cytokinesis begins, pinching the cell in two in a process called cleavage. 

Once cytokinesis is complete, two new, smaller cells are remaining.  Since replication occurred before the muscle cell divided, each new cell will have the same 20 chromosomes, exactly like its parent.