Biology: The Cell Cycle POGIL

If a culture in lab starts with one human cell, how many cells will there be after 24 hours?

2 cells

How many phases are in the cell cycle?

4 phases

Keeping in mind the events of each part of the cell cycle, mark with a double arrow on Model 1 where those cells might (either temporarily or permanently) exit the cell cycle to G0. Label this as G0. Why did you choose this location for G0? Hint: think of a place in the cell cycle where the cell is functioning normally, but not preparing to divide.

According to Abhinandan Surgonda Patil of the International Rice Research Institute, G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle.

Cancer, the uncontrolled growth of cells, often results in a tumor, or mass of abnormal cells. Some cancerous tumors consist of many cells that are much smaller than normal. According to Model1, what part(s) of the cell cycle is (are) most likely affected?

According to Model 1, G1 phase is most likely affected.

In Model 1, if the length of the arrow represents time, then for those cancerous cells, what happens to the time that is necessary for the cell cycle? What implications might this have for doctors who are treating cancer patients?

According to Model 1, the length of the arrow represents time. If some cancerous cells are smaller than normal than the time spent to make a cancerous cell would be shorter. Cancerous cells divide very quickly which makes it hard for doctors to treat.

What is the key process of Gap 1?

Cell division

In Model 2, what is the key process for Gap 1?

Cell increases in size

Looking again at Model 2, compare the amount of DNA at the beginning and at the end of synthesis. Why did the amount of DNA change?

Comparing the amount of DNA from G1 to end of synthesis, the amount of DNA doubled because DNA replicated.

What is the key process of Synthesis?

DNA Replication(chromosomes duplicate)

Ultraviolet light may cause DNA damage, which is known as a mutation. How might such damage affect events taking place during the synthesis phase? Hint: Use information from Model 2.

DNA would not be able to copy itself. It is important for DNA to copy itself so each new cell has an exact copy of DNA as part of the cell during Synthesis (S phase).

Other than cytokinesis, what else occurs during the mitosis phase? Hint: Consider the sets of DNA in each cell.

During mitosis phase, cytokinesis occurs, DNA is separated and the nucleus is split in half.

Model 2 presents cell cycle data for a typical human cell in culture. Use the phase names in Model 2 to label the G, M, and S phases in Model 1.

G is in Gap 1 and Gap 2, M is mitosis, S is Synthesis

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. Explain this observation using what you have learned about the cell cycle.

G0 phase hold cells that have completed M but not yet entered G1, as seen with many liver cells, whose maintenance in G0 is by a concentration of "quorum" protein, the loss or dilution of which releases just that number of cells from G0 into G1 to replace losses of liver cells such as those induced by a partial hepatectomy (liver) or haemorhage (bone marrow). Brain cells are super sensitive and very vulnerable nerve cells in your brain (e.g. neurons) that do not renew themselves or divide at all. There are very few exceptions to this rule - new neurons (brain cells) develop in the hippocampus through a process called neurogenesis.

During which phase does the size of the cell increase?

G1 phase

What is the order of the stages of a cell's life?

G1, S, G2, M

Imagine 100 cells were chosen randomly fro 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.

Given 100 randomly chosen cells, one would expect to find the largest number of cells in G1 phase because cells spend most of their time growing before making new cells.

How might the DNA damage go on to affect the rest of the cell cycle if apoptosis did not occur?

If apoptosis did not occur, damaged DNA replication would pass to daughter cells.

What could happen, after several cell cycles, to an organism whose damaged cells did not go through apoptosis? In other words, what if a damaged cell that is supposed to die does not?

If apoptosis does not occur or if a damaged cell does not die, damaged cells can cause health issues in an organism.

Why might it be beneficial to an organism for damaged cells to enter G0 instead of dividing once they exist?

It would be beneficial to an organism for damaged cells to enter G0 instead of dividing once they exist because the damaged cells would not create more damaged cells.

Looking at the third column of Model 2, compare the time spent in mitosis with the time spent in gap1, in human cells and describe any difference.

Model 2 showed that the time spent in mitosis is shorter than Gap1, mitosis takes 1/10 of the time in Gap1.

Identify two ways that the growth of an organism can be accomplished through the events of the cell cycle.

Organism growth requires more cells to grow and cells increase in size.

What is the key process for Synthesis in Model 2?

Replication (chromosome duplication)

Part A: Consider a cell in G0. Use the information in Model 1 and Model 2 to answer the following questions: in order for this cell to divide normally, what would need to occur?

Synthesis, G2 and mitosis need to occur in order for the cell to divide normally.

Cyto = cell, kinesis = cutting. What do you think takes place during cytokinesis?

The cell gets split in half during cytokinesis.

if a starfish sustains damage to a limb, it often grows a new one. if a human adult sustains damage to his or her spinal cord, mobility is often impaired. if a gecko looses its tail, it may grow a new one. Which type of cell is less like to go through the cell cycle after being damaged; a starfish limb, human spinal cord, or gecko tail?

The human spinal cord would be less likely to go through the cell cycle after being damaged because the human spinal cord becomes impaired, meaning that the cells do not regenerate like the starfish limb or gecko tail.

Is the original cell "dead" or does it disappear after mitosis?

The original cell does not die or disappear after mitosis because the original cell is split into two new cells (daughter cells) when the cell goes through the cell cycle again.

Part B: Consider a cell in G0. Use the information in Model 1 and Model 2 to answer the following question: what if the phase(s) you identified in part a of this question did not occur? What would be the outcome for the cell in that case?

The outcome would probably be that the cell just stays in G0.

The total time for the phases listed in Model 2 is 24 hours. How many human cells will be in the culture after another 24 hours. Explain.

There will be 4 human cells because the cells would divide.

According to Model 3, ultraviolet light is affecting a cell in which phase of the cell cycle?

Ultraviolet light affects G1 phase of the cell cycle according to Model 3.

During which phase does the number of cells increase?

at the end of mitosis