Chapter 6 Section 2Cell Cycle

The Life of a Eukaryotic Cell

The Cell Cycle◦The cell cycle is a

repeating sequence of cellular growth and division during the life of an organism.

◦A cell spends 90 percent of its time in the first three phases of the cycle, which are collectively known as the interphase.

The Cell CycleThe five

phases of the cell cycle are:◦First growth

(G1) phase: Cell grows

rapidly Cell carries

out routine functions

The five phases of the cell cycle are:Synthesis (S) phase:

◦DNA is copied

The five phases of the cell cycle are:

Second growth (G2) phase:◦Cell continues to

grow◦Cell prepares to

divide its nucleus

The five phases of the cell cycle are:

Mitosis◦Process that the

nucleus divides into two nuclei.

The five phases of the cell cycle are:Cytokinesis

◦Process that equally divides the cytoplasm

◦Pinches the parent cell into two new daughter cells

Control of the Cell CycleThe cell has key

checkpoints (inspection points) at which feedback signals from the cell can trigger the next phase of the cell cycle.

Control of the Cell CycleOther feedback

signals can delay the next phase to allow for completion of the current phase (yellow or red light).

Control of the Cell CycleControl occurs at

three principal checkpoints:◦Cell growth (G1)

checkpoint: Is the cell too big?

If yes, the cell will prepare to divide

If no, the cell will continue to grow.

Control occurs at three principal checkpoints:

DNA synthesis (G2) checkpoint:◦Is the DNA properly

replicated: If yes, mitosis will

occur. If no, DNA will

repaired.

Control occurs at three principal checkpoints:Mitosis

checkpoint:◦Did the nucleus

properly divide? If yes, cytokinesis

will occur. If no, mitosis

must be completed.

When Control is Lost: CancerCertain genes

contain the information necessary to make the proteins that regulate cell growth and division.

When Control is Lost: Cancer

If one of these genes is mutated, the protein may not function, and regulation of cell growth and division can be disrupted.

Cancer: the uncontrolled growth of cells.