11

key concepts

11.1

All Cells Derive from Other Cells

11.2

The Eukaryotic Cell Division Cycle Is Regulated

11.3

Eukaryotic Cells Divide by Mitosis

11.4

Cell Division Plays Important Roles in the Sexual Life Cycle

11.5

Meiosis Leads to the Formation of Gametes

11.6

Cell Death Is Important in Living Organisms

11.7

Unregulated Cell Division Can Lead to Cancer

Immortal Cells

On January 29, 1951, 30-year-old Henrietta Lacks visited the nearby Johns Hopkins Hospital in Baltimore, Maryland, because she had been bleeding abnormally after the birth of her last child. The physician found the reason for the bleeding: a tumor the size of a quarter on her cervix. A piece of the tumor was sent to a pathologist in a clinical laboratory, who reported that the tumor was malignant.

A week later Ms. Lacks returned to the hospital, where physicians treated her tumor with radiation to try to kill it. But before the treatment began, they took a small sample of cells and sent them without her permission—a practice common then but not ethical today—to the research lab of George and Margaret Gey, two scientists at the hospital who had been trying for 20 years to coax human cells to live and multiply outside the body. If they could do so, they thought, they might find a cure for cancer. The Geys hit pay dirt with Lacks’s cells; they grew and reproduced more vigorously than any cells they had ever seen and were given the name “HeLa cells.” Unfortunately, they also grew fast in Lacks’s body, and in a few months they had spread to almost all of her organs. Lacks died on October 4, 1951.

Because of their robust ability to reproduce, HeLa cells quickly became a staple of cell biology research. In controlled settings they could be infected with viruses, and they were instrumental in developing the supply of polioviruses that led to the first vaccine against that dread disease. HeLa cells have been used for important basic and applied research ever since, especially on the ways that human cells reproduce by cell division. Although Lacks had never been outside Virginia and Maryland, her cells have traveled all over the world and even into space on the space shuttle. Over the past 60 years, tens of thousands of research articles have been published using information obtained from Lacks’s cells. You’ll study one of them in this chapter.

Understanding the cell division cycle and its control is clearly an important subject for understanding cancer. But cell division is not just important in medicine. It underlies the growth, development, and reproduction of all organisms.

What controls the reproduction of cancer cells?