Which of the following statements about how fruit flies can develop an eye in the middle of a leg is true?

Question

(a) When the Ey gene is expressed in adult leg cells, these cells de-differentiate and become eye cells.
(b) The Ey gene encodes a transcription regulator that is the only transcription regulator used to produce a fruit-fly eye.
(c) When the Ey gene is introduced into cells that would normally give rise to a leg, the transcription regulators used to control its expression in the leg are different from those that are normally used to control Ey expression in the eye.
(d) All the eye cells found in the adult leg are a single cell type and have identical characteristics.

Answer 1

(c) In order to express Ey in cells that would normally become a leg, scientists must use a different promoter (and thus, involve different transcription regulators) to force Ey expression in an inappropriate cell. In this experiment, Ey is expressed in the embryo in leg-cell precursors, and so the transformation into eye tissue does not involve de-differentiation and re-differentiation [choice (a)]. When Ey is expressed in the leg-cell precursors, the Ey transcriptional regulator controls the expression of many different genes, including other transcription regulators that assist in regulating genes important for differentiation into an eye [choice (b)]. When Ey is expressed in the leg-cell precursors, an entire organ of several different cell types will develop [choice (d)].