A researcher observes two animal cells, Cell X and Cell Y, and records the following parameters: Cell X: Metabolically active, non-proliferating, DNA content is 2C, and possesses a single centrosome. Cell Y: Metabolically active, possesses an intact nuclear envelope, DNA content is 4C, and has two centrosomes in the cytoplasm. Identify the most likely cell cycle phases of Cell X and Cell Y respectively.

Step-by-step solution

Cell X has a DNA content of 2C and a single centrosome, indicating it has not undergone the S phase. Since it is non-proliferating but metabolically active, it is in the quiescent stage or G₀ phase. Cell Y has a DNA content of 4C and two centrosomes, indicating it has successfully completed the S phase where DNA replication and centrosome duplication occur. The presence of an intact nuclear envelope confirms it is still in interphase and has not entered the M phase (where the nuclear envelope disintegrates). Thus,