Before a cell can divide by mitosis, DNA synthesis has to take place. Following DNA synthesis, the DNA is separated into each half of the cell and then the cell divides.

The graph below shows the DNA content per cell over a period of time.

Which of the letters on the graph represent the sequence of the three events described above?

Answer:

DNA synthesis doubles the DNA content in the cell so the content will increase from 1 to 2 arbitrary
units, which is M. The DNA separates within the cell but the total content is still 2, so this is N or J.
The cell divides in half thus halving the DNA content per cell back to 1, which is K.
The answer is D