5c & d: Checkpoints in the Cell & Cancer

Checkpoints

While preparing for division, a cell does a self-check to see if everything is proceeding as normal.

A cell will not divide if: There are not enough nutrients available to support

continued growth The DNA has not been replicated The DNA is damaged

If an issue is detected the cell either repairs or destroys itself.

Checkpoints

Chromosomes attached to spindle fibers?

Chromosomes split evenly during anaphase?

Enough nutrients to support cell?

Damaged DNA?

DNA replicated?

Damaged DNA?

Cancer

If a mutation occurs in a gene that produces instructions for a checkpoint protein, cell cycle control will be lost.

Damaged cells divide without control – uncontrolled division is called cancer.

Instead of division stopping after a single layer of cells is produced, cancer cells grow in multiple layers called a tumor

Cancer

Cancer cells are abnormal and do not carry out the normal functions of the tissue where the tumor has grown

Cancer cells have large abnormal nuclei due to uncontrolled cell division from lack of regulation by checkpoints

Cancer cells attract blood vessels to supply the tumor with nutrients for continued growth

Some cancer cells can enter the blood stream and spread to other parts of the body and form new tumors – Metastasize