the chromosomes are attached to the spindle fibers. The spindle fibers will later pull the
chromosomes into alignment.
During metaphase, the chromosomes line up across the center of the cell. The chromosomes
line up in a row, one on top of the next. During anaphase, the two sister chromatids of each
chromosome separate, resulting in two sets of identical chromosomes. During telophase,
the spindle dissolves and nuclear envelopes form around the chromosomes. The drawings
of Figure5.4show this process. This is further shown inFigure5.5. Each new nucleus
contains the exact same number and types of chromosomes as the original cell. The cell
is now ready for cytokinesis, producing two genetically identical cells, each with its own
nucleus.
Lesson Summary
- Cellsdivideforgrowth, development, reproductionandreplacementofinjuredorworn-
out cells. - The cell cycle is a serious of regulated steps by which a cell divides.
- During mitosis, the newly duplicated chromosomes are divided into two daughter nu-
clei.
Review Questions
- In what phase of mitosis are chromosomes moving toward opposite sides of the cell?
- In what phase of mitosis do the duplicated chromosomes condense?
- What step of the cell cycle is the longest?
- What is the term for the division of the cytoplasm?
- What happens during the S stage of interphase?
- Interphase used to be considered the “resting” stage of the cell cycle. Why is this not
correct? - What are some reasons that cells divide?
- During what stage of the cell cycle does the cell double in size?
- Why must cell division be tightly regulated?
- What is the purpose of mitosis?
Further Reading / Supplemental Links