Editing genes shouldn’t be too scary — unless they are the ones that get passed to future generations

Gene editing is one of the scarier things in the science news, but not all gene editing is the same. It matters whether researchers edit “somatic” cells or “germline” cells.

Germline cells are the ones that propogate into an entire organism – either cells that make sperm and eggs (known as germ cells), or the cells in an early embryo that will later differentiate into different functions. What’s critical about those particular cells is that a change or mutation in one will go on to affect every cell in the body of a baby that grows from them. That’s why scientists are calling for a moratorium on editing the genes of germ cells or germline cells.

Somatic cells are everything else – cells in particular organs or tissues that perform a specific function. Skin cells, liver cells, eye cells and heart cells are all somatic. Changes in somatic cells are much less significant than changes in germline cells. If you get a mutation in a liver cell, you may end up with more mutant liver cells as the mutated cell divides and grows, but it will never affect your kidney or your brain.

Our bodies accumulate mutations in somatic tissues throughout our lives. Most of the time humans never know it or suffer any harm. The exception is when one of those somatic mutations grows out of control leading to cancer.

I am a geneticist who studies the genetic and environmental causes of a number of different disorders, from birth defects – cleft lip and palate – to diseases of old age like Alzheimer’s. Studying the genome always entails thinking about how the knowledge you generate will be used, and whether those likely uses are ethical. So geneticists have been following the gene editing news with great interest and concern.