Marina Melixetian and her colleagues suppressed the expression of Geminin protein in human cells by treating the cells with small interfering RNAs (siRNAs) complementary to Geminin messenger RNA. Forty‑eight hours after treatment with siRNA, the Geminin‑depleted cells were enlarged and contained a single giant nucleus. Analysis of DNA content showed that many of these Geminin‑depleted cells were 4n or greater.
Explain these results.