Name Student Response sheet Period. Cell Division Mitosis Lab

Transcription

1 ame Student Response sheet Period Cell Division Mitosis Lab Modeling Mitosis (Refer to your summary sheets from Mitosis & Meiosis on the Table ) Part 1: Effects of Environment on Mitosis Questions: 1. State your null and experimental hypotheses for this investigation. (Remember why it is called a ULL hypothesis...) Ho: Ha: Counting Cells and Analyzing Data Table 1a: Onion Root Tip Cell Phase Data; group B Photo Plates Tip Trials 1 (Card # ) 2 (Card # ) 3 (Card # ) umber of Cells Mitotic Table 1b: Onion Root Tip Cell Phase Data; group A Photo Plates Tip Trials 1 (Card # ) 2 (Card # ) 3 (Card # ) umber of Cells Mitotic 1. Collect the total class data and enter the values into Table 2; these are the observed values for all groups. Table 2: Collected Class s of Observed Values (o) (Enter on Smart Board) Mitotic 1

2 Table 3: Table of Formulas for Expected Values (e) Mitotic A B A + B C D C + D A + C B + D A + B + C + D = 2. Use the Observed Values totals (o) from Table 2 to calculate the Preliminary Expected Values using the formulas from Table 3 to calculate the Preliminary Expected Values, record in Table 4. Table 4: Table of Preliminary Values for Calculating Expected Values Mitotic 3. Use the Preliminary Expected Values from Table 4 to calculate the Expected Values (e) from the formulas in Table 5. Record in Table 6. Table 5: Formula of Expected Values (e) (A + B)(A + C) (C + D)(A + C) Mitotic (A + B)(B + D) (C + D)(B + D) Table 6: Table of Expected Values (e) Mitotic 4. Enter the Observed Values (o) from Table 2 and Expected Values (e) from Table 6 for each group into Table 7. Calculate the chi-squared (Χ * ) value for the data by adding together the numbers in the right column 2

3 Table 7: Calculation of the Chi-Square Value o e (o e) (o e) 2 (o e) 2 e Mitotic Mitotic of (+,-). - = chi-squared (Χ * ) = 5. Compare chi-squared (Χ * ) value to the critical value in Table 8. Table 8: Critical Values of Chi-Square Distribution p value Degrees of Freedom The degrees of freedom (df) equals the number of treatment groups minus one multiplied by the number of phase groups minus 1. In this case there are two treatment groups (control, treated) and two phase groups (interphase, mitosis); therefore, df = (2-1)(2-1) = The p value is 0.05, and the critical value 3.84 (find this on Table 8). If the chi-square value is greater than or equal to this critical value, the null hypothesis is rejected. If the calculated chi-squared value is less than this critical value the null hypothesis is not rejected. 3

4 Conclusions Did you accept or reject your null hypothesis? Did the fungal pathogen lectin increase the number of cells in mitosis? Use your statistical analysis to completely and correctly answer this question. Part 2: Loss of Cell Cycle in Cancer Background Information Many of us have family members who have or have had cancer. Cancer can occur when cells lose control of their cell cycle and divide abnormally. This happens when tumor suppressor genes, such as p53 or Rb (retinoblastoma), are mutated. There are many questions you should consider before beginning your investigation. Review from Part 1 1. How is the cell cycle controlled in normal cells? 2. What are cyclins and cyclin-dependent kinases? What do these proteins do in a cell? 4

5 Prelab Questions for Part 2 3. How are normal cells and cancer cells different from each other? 4. What are the main causes of cancer? 5. What goes wrong during the cell cycle in cancer cells? 6. What makes some genes responsible for an increased risk of certain cancers? 7. Do you think that the chromosomes might be different between normal and cancer cells? The last question 7, is the focus of this part of the lab. 8. Write a one-sentence hypothesis as to how the chromosomes of a cancer cell might appear in comparison to a normal cell and how those differences are related to the behavior of the cancer cell. For the following case, look at the pictures of chromosomes (karyotypes) from normal human cells and HeLa cervical cancer cells and compare them. Or use a Google image search (suggestion cancer cell karyotype is a good starting point). Count the number of chromosomes in each type of cell, and discuss their appearance. Then answer the following questions. 9. Do your observations support your hypothesis? 10. If not, what type of information might you need to know in order to understand your observations? 11. If yes, what type of information can you find that would validate your conclusions? 5

6 Case 1: HeLa cells HeLa cells are cervical cancer cells isolated from a woman named Henrietta Lacks. Her cells have been cultured since 1951 and used in numerous scientific experiments. Henrietta Lacks died from her cancer not long after her cells were isolated. Lacks s cancer cells contain remnants of human papillomavirus (HPV), which we now know increases the risk of cervical cancer. You may wish investigate these resources. The Immortal Life of Henrietta Lacks by Rebecca Skloot. Alternatively, check out her Wikipedia page. Loss of Cell Cycle and Cancer (p. 246 in Campbell 10th edition) Henrietta Lacks Video HeLa Karyotype ginalimages/karyotype.jpg Answer the following: 12. From your observations, what went wrong in Henrietta Lacks s cervical cells that made them cancerous? 13. How does infection with human papillomavirus virus (HPV) increase the risk of cervical cancer? 14. Your take: Should tissue be removed from a patient without his or her consent for research? Why? 15. How was the HeLa cell line cultured? 16. What virus infected Henrietta Lacks and may have caused her cervical cancer? What cellular process is affected by this virus? 6

7 17. Was there bias in the way Henrietta Lacks was treated at Johns Hopkins? 18. Put the use of HeLa cells on trial. Debate what is more important: an individual s rights to his/her own body tissues or the medical knowledge gained by studying a patient s tissues? 19. Should Henrietta Lacks s family be compensated for the discoveries made using her cells? 20. Do companies or universities have the right to patent discoveries made using a patient s tissues or genes without consulting the patient? 21. What other legal and ethical questions are raised by this case? 7