Biology Cell Cycle Quiz

Period of activity in which cells do most of their growing. During this phase cells increase in size and synthesize new proteins and organelles.

Phase in which chromosomes are replicated and the synthesis of DNA molecules takes place. Key proteins associated with the chromosomes are also synthesized during the S phase. Usually, once a cell enters the S phase and begins the replication of its chromosomes, it completes the rest of the cell cycle.

G2 is usually the shortest of the three phases of interphase. During the G2 phase, many of the organelles and molecules required for cell division are produced.

The process of cell division, which is divided into four phases, prophase, metaphase, anaphase and telophase.

During prophase, the chromosomes become visible. The centrioles two tiny structures located in the cytoplasm near the nuclear envelope, separate and take up positions on opposite sides of the nucleus.The centrioles lie in a region called the centrosome that helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes. During prophase, the condensed chromosomes become attached to fibers in the spindle at a point near the centromere of each chromatid.

During metaphase, the chromosomes line up across the center of the cell. Microtubules connect the centromere of each chromosome to the two poles of the spindle.

During anaphase, the centromeres that join the sister chromatids split, allowing the sister chromatids to separate and become individual chromosomes. The chromosomes continue to move until they have separated into two groups near the poles of the spindle. Anaphase ends when the chromosomes stop moving.

In telophase, the chromosomes, which were distinct and condensed, begin to disperse into a tangle of dense material. A nuclear envelope re-forms around each cluster of chromosomes. The spindle begins to break apart, and a nucleolus becomes visible in each daughter nucleus. Mitosis is complete.