Bio Chp 7-Cell Cycle, Mitosis & Cancer

Review of chromosomes, cell cycle, mitosis, cytokinesis, cell-cycle checkpoints, cancer cells, tumors, metastasis, angiogenesis, chemotherapy, and radiation.

Normal chromosome number in human body cells

46 chromosomes, arranged in 23 pairs.

Purpose of mitosis

Produces genetically similar body cells for growth, repair, and replacement.

Cell cycle

The ordered sequence of growth, DNA replication, and cell division.

Major stages of the cell cycle

G1, S, G2, M phase, and cytokinesis.

G1 phase

The cell grows, performs normal functions, and prepares for DNA replication.

S phase

DNA is replicated so each chromosome is copied.

G2 phase

The cell continues growing and prepares for mitosis.

M phase

The phase that includes mitosis: prophase, metaphase, anaphase, and telophase.

Mitosis

Division of the nucleus that separates duplicated chromosomes into two nuclei.

PMAT

Prophase, Metaphase, Anaphase, Telophase.

Prophase

Chromosomes condense, the spindle begins forming, and the nuclear envelope breaks down.

How to recognize prophase

Condensed chromosomes are visible but are not lined up at the cell's middle.

Metaphase

Chromosomes line up at the middle of the cell.

How to recognize metaphase

Chromosomes are arranged along the cell's equator or metaphase plate.

Anaphase

Sister chromatids separate and move toward opposite poles.

How to recognize anaphase

Chromatids appear to be pulled apart toward opposite sides of the cell.

Telophase

Chromosomes reach opposite poles and new nuclear envelopes form.

How to recognize telophase

Two groups of chromosomes are at opposite ends and two nuclei begin to appear.

Cytokinesis

Division of the cytoplasm to form two separate daughter cells.

Animal-cell cytokinesis

A cleavage furrow pinches the cell membrane inward.

Plant-cell cytokinesis

A cell plate forms between the daughter cells and develops into a new cell wall.

Plant vs. animal cytokinesis

Animals use a cleavage furrow; plants form a cell plate.

Result of mitosis and cytokinesis

Two genetically similar daughter cells with the same chromosome number as the original body cell.

Cell-cycle checkpoint

A control point where the cell checks whether conditions are suitable before continuing.

Purpose of cell-cycle checkpoints

Help prevent damaged or abnormal cells from dividing.

G1 checkpoint

Checks cell size, nutrients, growth signals, and DNA damage before DNA replication.

G2 checkpoint

Checks whether DNA replication is complete and whether DNA is damaged before mitosis.

M checkpoint

Checks that chromosomes are properly attached to spindle fibers before separation.

Cancer

A disease involving uncontrolled cell division caused by loss of normal cell-cycle regulation.

Cancer cell vs. normal cell

Cancer cells divide uncontrollably and may ignore signals that normally stop cell division.

Contact inhibition

The tendency of normal cells to stop dividing when they come into contact with neighboring cells.

Cancer and contact inhibition

Cancer cells may lose contact inhibition and continue dividing even when crowded.

Benign tumor

A noncancerous growth that remains localized and does not invade nearby tissues.

Malignant tumor

A cancerous growth that can invade nearby tissues and may spread to other parts of the body.

Metastasis

The spread of cancer cells from the original tumor to other parts of the body.

Angiogenesis

Formation of new blood vessels; tumors can stimulate this process to obtain nutrients and oxygen.

Diapedesis

Movement of cells through blood-vessel walls; cancer cells can use this ability during metastasis.

Chemotherapy

Treatment that uses drugs to kill or slow rapidly dividing cancer cells.

Radiation therapy

Treatment that uses high-energy radiation to damage DNA and kill or stop cancer cells.

Why chemotherapy can affect healthy cells

It can also damage normal cells that divide rapidly.

Why radiation can damage cancer cells

Radiation damages DNA, making it difficult for cancer cells to keep dividing.

Primary tumor

The original site where a cancer begins.

Cancer and checkpoints

Cancer cells can bypass or ignore normal checkpoint controls and continue dividing despite damage.

Mitosis in growth and repair

Mitosis increases cell number during growth and replaces damaged, worn-out, or dead cells.