The Song of the Cell: An Exploration of Medicine and the New Human

by Siddhartha Mukherjee

His trip to the United States across war-shredded Europe was a harrowing pilgrimage. He traveled through bleak, desolate Poland, where he was detained for weeks awaiting immigration.

The nucleus is the command center; the captain’s bridge of the cell. It is the place that both receives and then disseminates most of life’s signals. RNA, the code to build proteins, is copied from the genetic code here and then exported out of the nucleus. We might imagine the nucleus as the center of the center of life.

The nucleus, as I mentioned before, houses the organism’s genome, made of long stretches of deoxyribonucleic acid. The DNA double helix is elaborately folded and packaged around molecules called histones, and tightened and wound further into structures called chromosomes.

In short: a cell’s autonomy lies in its anatomy.

Jared had lost sight but found sound.

But the retina is a special site. Not only is a raindrop’s worth of virus sufficient to infect the cells, but also the retina is uniquely immune privileged: along with a few other places in the body—the testes, among them—it is not actively surveyed by an immune response and therefore highly unlikely to generate a severe reaction to an infectious agent.

Mitochondrial mutations are special because they can be inherited only from your mother, while most other mutations can come from either parent. Mitochondria don’t have an autonomous existence; they can live only inside cells. They divide when a cell divides and then are apportioned to the two daughter cells. When an egg cell forms in the mother, all its mitochondria are from her cells. Upon fertilization, the sperm cell injects its DNA into the egg—but not any mitochondria. Therefore, every mitochondrion that you are born with is maternal in origin. The mutation in the mtND4 gene that Jared inherited had to come from his mother. It is likely that it occurred by chance, during the creation of the egg, because his mother did not have the disease.

Not every cell is capable of reproducing: some cells, such as some neurons, have undergone permanent or terminal division and will never divide again.

In humans and multicellular organisms, the process for the production of new cells to build organs and tissues is called mitosis—from mitos, the Greek word for “thread.” In contrast, the birth of new cells, sperm, and eggs for the purpose of reproduction—to make a new organism—is called meiosis, from meion, the Greek word for “lessening.”

Looking but not seeing. Sight—real sight—requires insight.