What is Differentiation, determination, potency?

A cell is differentiated when it expresses the stable pattern of genes — and so the proteins, shape and function — of one cell type. It is determined (or committed) when its fate is fixed although its differentiation has not yet begun: a myoblast looks like a fibroblast but will make only muscle. Potency is the range of types a cell can still give: totipotent (the zygote and first blastomeres, which make everything including the placenta), pluripotent (the inner cell mass, which makes every tissue of the body), multipotent (a stem cell of the blood or of muscle, which makes the types of one tissue), unipotent. A stem cell is a cell that divides to give one daughter like itself and one that goes on to differentiate, which keeps the stock while supplying the tissue. Differentiation is in most cases not a loss of genes but a choice among them: the genome of a muscle nucleus is complete.