Question

In Figure 12.14, why do the nuclei resulting from experiment 2 contain different amounts of DNA?

Short answer

Nuclei resulting from experiment 2 contain different amounts of DNA because the nucleus that was fused with the nucleus undergoing the M phase or dividing phase skipped the S phase that replicates the DNA.

It jumped from the G1 phase to the M phase skipping the S phase due to induction by cytoplasmic molecules that control the cell cycle at the mitotic phase.

Step-by-step solution

DNA

DNA is the main hereditary material inherited to the next generations and maintains cell integrity while dividing.Its content changes with the events occurring in the cells like the S phase, mitosis, and meiosis. It is the main ingredient that is distributed to the daughter cells in the form of chromosomes.

Control of cell cycle

The cell cycle is controlled by some specific cytoplasmic molecules that signal the different phases of the cell cycle.

All events in the cell cycle occur in a sequence that is due to a control system of the cell cycle involving molecules that work cyclically to coordinate all events of the cell cycle. There are three main checkpoints in the cell cycle that are controlled by these molecules.

Stimulation of division by cytoplasmic molecules 

In experiment 2, the cell of G1 is fused with the cell in the dividing phase. The resulting cell of G1 initiated division due to the influence of cell cycle control molecules, and it skipped the step of DNA replication in the S phase.

So the DNA is not doubled in this cell, but the cell that was in the M phase from initiation contains a doubled amount of DNA compared to the cell that started division after fusion. So the resulting nuclei have different amounts of DNA.