Lab 7 - Cell Division: Mitosis and Meiosis
2.Pre lab questions :
1. How did you develop from a single-celled zygote to an organism with trillions of cells? How many mitotic cell divisions would it take for one zygote to grow into an organism with 100 trillion cells?- my cells went through mitosis 100 trillion times.2. How is cell division important to a single-celled organism?-It lets single celled organisms like bacteria reproduce asexually.3. What must happen to ensure successful cell division?- the cell must go through the three main phases, interphase, mitosis, and cytokinesis. The cells DNA must be replicated, and it must pass through the three main checkpoints successfully. 4. How does the genetic information in one of your body cells compare to that found in other body cells?- They are the same; each cell in my body has the same genetic information.5. What are some advantages of asexual reproduction in plants?-It is simpler; it can be done by a single plant. They will also have the same genetic code because there is no partner.6. Why is it important for DNA to be replicated prior to cell division?- It has to make sure the process was done correctly; it hits checkpoints, if there is a problem, the cell cycle stops before actually division, causing an array of issues7. How do chromosomes move inside a cell during cell division?- chromosomes use mitosis spindles to move inside a cell8. How is the cell cycle controlled? What would happen if the control were defective?- it's controlled by a series of checkpoints (3 main ones). If the control were defective, the cells may reproduce uncontrollably, they also may create abnormal cells. #5 how cell division is controlled:Cell division is controlled by a series of complexes and checkpoints. Cell complexes contain CDKs and cycling, which pair together to turn on or off important cellular processes. (These are enzymes). Successful cell division also must pass a series of three main checkpoints. These checkpoints ensure that everything is going as planned. If there is a problem with the cell at that point, the checkpoint will detect it, and either stop the cell cycle or have the cell commit apoptosis. The g1 checkpoint ensures that the cell is stimulated by appropriate external growth factors like PDGF. The g2 checkpoint checks for damage after the DNA has already been replicated. Finally the M Spindle checkpoint makes sure that the mitotic spindle fibers are attached to he kinetochores. 6. Explain how eukaroytic cells divide to produce genetically identical cells. You do not need to know the names of the stages just the general way the process works, chromosome duplication, centromere, sister chromatids etc.- The cell grows and the DNA is copied first; during interphase. During mitosis, the replicated sister chromatids are then separated. A centromere holds two sister chromatids together. Mitosis produces two daughter cells. Cytokinesis separates them from each other. 7. Add answers to the questions on page S87 of the lab manual
If a cell contains a set of duplicated chromosomes, does it contain any more genetic information than the cell before the chromosomes were duplicated
-No it does not contain any more genetic information than before the cell chromosomes were duplicated. The genetic information is exactly the same.
What is the significance of the fact that chromosomes condense before they are
- They become stronger, and can move easier.
How are the chromosome copies, called sister chromatids, separated from each
- They are separated from each other during mitosis when the spindle fibers pull them apart
What would happen if the sister chromatids failed to separate?
- Cell division wouldn't be completed properly; it may result in a mutation in the daughter cells.Part 2
You have been asked to investigate whether the fungal pathogen lectin affects the
number of cells undergoing mitosis in a different plant, using root tips.
What is your experimental hypothesis? Your null hypothesis? Are these the same?- My experimental hypothesis is that exposure to lectin protein will cause the onion root tips to go through mitosis at a quicker rate. My null hypothesis is that the lectin exposure will not affect the number of cells going through mitosis. No they are not the same. An experimental hypothesis is what you expect to happen based off of scientific knowledge. A null hypothesis proposes the idea that there's no significance between the two variables that help to prove anything.
How would you design an experiment with onion bulbs to test whether lectins
increase the number of cells in mitosis?
I would use two different groups of onion bulbs. One being exposed to the lectin, and one not. In one jar I would put the onion's roots in sand which contains the lectin. In the other jar I would just put the onion in the sand (with no lectin). Both jars will be provided with water.
What would you measure, and how would you measure it?
We would measure the number of cells that are going through mitosis ans the number of cells that are in interphase, in both the experimental and control group. We would measure it by looking under a microscope and counting sections of the onion cells.
What would be an appropriate control for your experiment?
- An appropriate control for the experiment would be to have no exposure to the pathogen lectin.#8 (design the experiment)#9 A null hypothesis is a hypothesis which shows no relationship in the given set of data. The data collected shows no significance and is due to chance. The chi squared test is used to compare data that was collected to data that you would expect to collect based off of a hypothesis.Post lab review:
What was the importance of collecting the class data?
- The importance of collecting the class data was that it provided us with our observed data, and allowed us to compare it with the expected value. The more data we have, the more accurate our results are
Was there a significant difference between the groups?
- No there isn't a significant statistical difference between the control and the treated groups.
Did the fungal pathogen lectin increase the number of root tip cells
- No it did not increase the number of root tip cells in mitosis. It is shown that they both had the same number of 306 for the observed and and control under the mitosis section. Also the .97 value is much lower than the 3.94 value. The null hypothesis was excepted.
What other experiments should you perform to verify your findings?
Test lectin exposure on other plants besides onion root tips. Check to see if the null hypothesis is excepted for these trials as well.
Does an increased number of cells in mitosis mean that these cells are dividing faster
than the cells in the roots with a lower number of cells in mitosis?- No it does not mean that the cells in mitosis are dividing faster. It just means that there are More cells in that section. The rate of mitosis can't be determined by the number of cells in mitosis.
What other way could you determine how fast the rate of mitosis is occurring in root
We could test cells exposed to to lectin and not exposed to lectin, and them time how long is takes for them to go through mitosis. This would require close attention because we would have to know the exact time when the cells finish mitosis.