determination and commitment
/ dee-ter-mi-NAY-shun and kuh-MIT-ment /
Think of a student who has chosen a major but has not yet taken any of its classes. From the outside they look like any other student, yet their path is set: they are heading toward, say, becoming an engineer. Determination is the cell version of choosing the major — a cell has internally locked in what it will become, even before it visibly changes.
Precisely, determination (also called commitment) is the stage at which a cell's fate becomes fixed and self-perpetuating, before any obvious change in appearance. A committed cell will follow its chosen path even if you move it to a different part of the embryo. Biologists test for it by transplantation: a determined cell keeps becoming what it was committed to regardless of its new surroundings. Determination usually comes first; visible differentiation follows later as the cell actually builds its specialized features.
The distinction matters because it separates the decision from the outcome. A cell can be fully committed to becoming a neuron while still looking unremarkable, which means fate is often sealed earlier than it appears. Commitment is typically locked in by stable internal programs — master transcription factors and epigenetic marks — that keep the choice 'remembered' through every later cell division, so the lineage stays on track without needing to be told again.
If you transplant a patch of committed cells from one region of an early embryo to another, they often go on to form the structure they were destined for in their original location — proof that their fate was already determined before it was visible.
Transplant test: committed cells keep their fate even in a new neighborhood.
Determination (the locked-in decision) comes before differentiation (the visible change) — a committed cell may look ordinary for a while, so you cannot judge its fate by appearance alone.