The Cell Cycle

Discussion Question: Cells reproduce by mitosis (by dividing into two cells identical to the original). What are some things that would have to happen for a cell to copy itself?

Starting at the starred cell, what is the order of the stages of a cell’s life?

Consider your answer to Questions 3 & 4, identify two ways that the growth of an organism can be accomplished through the events of the cell cycle.

Looking at the third column of Model 2, compare the time spent in mitosis with the time spent in Gap 1 in humans cells and describe any difference.

Imagine 100 cells were chosen randomly from a tissue sample and examined under a microscope. In which phase of the cell cycle would you expect to find the largest number of cells? Explain.

Look again at Model 2. Compare the amount of DNA at the beginning and end of synthesis. Why did the amount of DNA change?

Write below the text that should go in the “Key Process” column for the synthesis phase in Model 2.

Look carefully at information given to you in Model 1 and Model 2. Fill in the key process column in the table for gap 1.

If a starfish sustains damage to a limb, it often grows a new one. If a gecko loses its tail, it may grow a new one. On the other hand, if a human adult sustains damage to their spinal cord, mobility is often impaired and never regained. Which type of cell is less likely to go through the cell cycle after being damaged – starfish limb, human spinal cord, or gecko tail? Support your answer.

Occasionally cells stop dividing and enter another phase, G₀. If you damage your liver, new liver cells can be produced to replace up to 75% of the liver. However, if you sustain brain damage, your body does not produce new brain cells. Which is more likely to be found in the G₀ phase, brain cells, or liver cells, and what is happening during the G₀ phase?

Which phase of the cell cycle would you expect G₀ to take place during? Explain your answer.