What term is used to describe cells that have not yet differentiated?

The correct term for cells that have not yet differentiated is stem cells. Stem cells are unique because they have the capacity to develop into many different cell types in the body. They are unspecialized cells that can give rise to specialized cells, such as neurons, muscle cells, and gametes, through a process known as differentiation. This ability is crucial in development, tissue repair, and regeneration.

In contrast, the other options refer to cells that have already undergone differentiation. Neurons are specialized cells of the nervous system responsible for transmitting signals. Muscle cells are specialized for contraction and movement. Gametes are reproductive cells, specifically sperm and eggs, that have also differentiated to fulfill specific roles in reproduction. Each of these cell types has a distinct structure and function, differentiating them from stem cells, which can transform into various types of cells depending on the needs of the body.