somatic

Meaning: Somatic (Greek soma, body) cells form the tissues and organs: skin, muscle, neurons, liver. They contrast with germ-line cells, which give rise to gametes by meiosis. Most somatic cells are diploid (2n) and divide by mitosis, producing genetically identical daughter cells. A somatic mutation can affect the individual, for example by contributing to cancer, but it is not passed to offspring through gametes. The same word also names the somatic nervous system, the part of the peripheral nervous system that carries voluntary motor commands to skeletal muscle, as opposed to the autonomic system.

On the MCAT: Expect questions that pair cell type with ploidy and division (somatic: 2n, mitosis; gametes: n, meiosis), or ask whether a mutation in a given tissue could be inherited. Cloning by somatic cell nuclear transfer places a somatic nucleus into an enucleated egg.

Common confusion: Students assume any mutation is heritable. The fact that settles it: a mutation must reach the germ line to be passed on through gametes. Also, "somatic" does not guarantee a nucleus or 2n: mature red blood cells lack a nucleus, and some somatic cells, such as certain liver cells, are polyploid.