CELLULAR REPRODUCTION

mad17743_ch08.qxd 3/9/06 3:47 age 62 8 VW ellular reproduction involves growth and cell division, which are the two major portions of the cell cycle. ell division involves mitosis and cytokinesis. ollowing mitosis, each daughter cell has the same number and kinds of chromosomes as the mother cell. he phases of mitosis and cytokinesis are studied in both animal and plant cells. When the cell cycle occurs repeatedly and is no longer regulated, cancer results. fter studying the key terms of this chapter, match the phrases below with the alphabetized list of terms. apoptosis cytokinesis cell cycle interphase centromere sister chromatid centrosome somatic cell chromatin spindle cyclin tumor a. body cell b. splitting of the cytoplasm following cell division c. microtubule organizing center d. series of events that occur as cellular growth occurs e. constriction where sister chromatids are joined f. results from uncontrolled growth g. half of a duplicated chromosome h. tangled network of threads in nucleus i. programmed cell death brought about by caspases j. protein that appears and disappears as the cell cycle occurs k. portion of the cell cycle in between cell divisions l. apparatus that accounts for chromosome movement during mitosis 62

mad17743_ch08.qxd 3/9/06 3:47 age 63 X tudy the text section by section as you answer the questions that follow. 8.1 B (. 112 113) ellular reproduction occurs as an organism becomes multicellular and as a tissue undergoes repair. n order for cellular reproduction to occur, chromosomes must be condensed so that they can be distributed to daughter cells. 1. ndicate whether these statements concerning chromosomes are true () or false (): a. he chromosomes that appear just before cell division begins consist of coiled and condensed chromatin. b. duplicated chromosome consists of two sister chromatids, each containing a double helix. c. chromosome contains, in addition to. d. chromosome contains and histones. 8.2 (. 114) uring interphase of the cell cycle, a cell duplicates its contents, including its chromosomes. uring the mitotic stage, a cell distributes its chromosomes to the daughter cells and divides the cytoplasm. ell division consists of mitosis and cytokinesis. itosis is division of the nucleus, and cytokinesis is division of the cytoplasm. 2. atch the letters in the following diagram to these phrases: itosis and cytokinesis occur. replication occurs as chromosomes duplicate. rowth occurs as organelles double. rowth occurs as the cell prepares to divide. ells can exit the cell cycle and enter an arrested stage. a. 1 b. e. cytokinesis telophase anaphase metaphase prophase nterphase 2 d. c. 63

mad17743_ch08.qxd 3/9/06 3:47 age 64 8.3 (. 115 118) ollowing mitosis, each daughter nucleus has the same number of chromosomes as the parent cell. nce cytokinesis has occurred following mitosis, two daughter cells are present. 3. tudy the following diagram and explain by answering the questions why replication must precede mitosis: chromosome consisting of one chromatid duplication duplicated chromosome mitosis centromere sister chromatids daughter chromosomes a. replication preceded the formation of what type of chromosome? b. duplicated chromosome consists of what two parts? c. When the sister chromatids separate, what results? d. f a cell has eight duplicated chromosomes during mitosis, how many daughter chromosomes are in each daughter nucleus? e. oes each daughter nucleus have the same number and kinds of chromosomes as the parent cell following mitosis? 4. abel the following diagram using the alphabetized list of terms: aster centriole centromere centrosome chromosome nuclear membrane fragment spindle fiber b. c. d. a. e. f. g. 64

mad17743_ch08.qxd 3/9/06 3:47 age 65 5. omplete the following diagram to show the arrangement and movement of chromosomes during animal cell mitosis. ame the phase (a-d) and briefly describe the events of each phase on the lines provided (e-h): e. f. a. b. g. h. c. d. 6. a. ow does an animal cell undergo cytokinesis? b. Which phases show the process of cytokinesis? 7. o show the difference between plant and animal mitosis, complete the following table by writing or no: ame phases pindle fibers ster ell plate urrowing itosis lant ell nimal ell 8. a. o plant cells have a centrosome? b. o plant cells have centrioles? c. re centrioles necessary to spindle formation? xplain. 65

mad17743_ch08.qxd 3/9/06 3:47 age 66 8.4 (. 119 120) he cell cycle is tightly controlled. he cell cycle can stop due to external signals, such as contact inhibition, or internal, such as inappropriate telomere length. cell that is no longer in the cell cycle is in 0 or undergoes apoptosis, programmed cell death. 9. atch the checkpoints in the following diagram to these phrases: a. poptosis can occur if is damaged beyond repair. b. itosis will not occur until has replicated. c. itosis stops until chromosomes are properly aligned. 1 checkpoint 1 0 checkpoint ontrol system 2 checkpoint 2 10. nternal and external signals control the cell cycle. lace the appropriate letter next to each statement. internal signal external signal a. cyclin, a protein that combines with a kinase before the phase and the phase of the cell cycle b. growth factors released by neighboring cells c. hormones delivered by the bloodstream d. telomeres, a sequence of repeating bases at the end of chromosomes 8.5 (. 121 123) he characteristics of cancer cells are associated with their ability to divide uncontrollably. t is possible to avoid certain agents that contribute to the development of cancer and to take protective steps to reduce the risk of cancer. 11. omplete the following table: haracteristics of ormal ells haracteristics of ancer ells ifferentiated cells a. ormal nuclei b. ontact inhibition c. ne organized layer in tissue culture d. 66

mad17743_ch08.qxd 3/9/06 3:47 age 67 12. nstead of growing in a. layer(s), as normal cells do, cancer cells grow in b. layer(s), losing the property of c. inhibition. ancer cells divide to form a growth, or d.. he cells of e. tumors remain in one place. he cells of f. tumors wander, a characteristic called g.. 13. atch the description to these types of cancer treatments: 1. radiation 2. chemotherapy 3. interferes with the functioning of the mitotic spindle 4. interferes with the reception of signals that stimulate growth 5. inhibits formation of blood vessels that serve the tumor a. kills cancer cells that are wandering about the body b. tamoxifen c. taxol d. antiagiogenic drug e. kills cancer cells that have not spread to a new location 14. ame three ways to prevent cancer from developing: a. b. c. 67

68 W eview key terms by searching for the following alphabetized list of terms and filling in the blanks below: J Z Z B B Z Q V J B J Q B W X Q J X V B W B J W J W J Q X W Z V Q W Z Q X W X centromere chromatin cytokinesis interphase mitosis prophase spindle telophase a. ype of cell division in which daughter cells receive the exact chromosome and genetic makeup of the parent cell; occurs during growth and repair. b. ivision of the cytoplasm following mitosis and meiosis. c. tages of the cell cycle ( 1,, 2 ) during which growth and synthesis occur when the nucleus is not actively dividing. d. angled mass of thin threads consisting of and associated proteins observed within a nucleus that is not dividing. e. icrotubule structure that brings about chromosomal movement during nuclear division. f. itosis phase during which chromatin condenses so that chromosomes appear. g. onstricted region of a chromosome where sister chromatids are joined and where the chromosome attaches to a spindle fiber. h. itosis phase during which daughter nuclei are forming. mad17743_ch08.qxd 3/9/06 3:47 age 68

mad17743_ch08.qxd 3/9/06 3:47 age 69 BJV Q o not refer to the text when taking this test. n questions 1 4, match the description to the phase. a. anaphase b. metaphase c. prophase d. telophase 1. hromosomes first become visible. 2. hromatids separate at centromere. 3. hromosomes are aligned at the metaphase plate. 4. ast phase of nuclear division. 5. he diploid chromosome number in an organism is 42. he number of chromosomes in its sperm and egg cells is normally a. 21. b. 42. c. 63. d. 84. 6. Which statement about mitosis is correct? a. does not affect the nuclear envelope b. forms four daughter cells c. makes diploid nuclei d. rophase is the first active phase. 7. ow does mitosis in plant cells differ from that in animal cells? a. nimal cells do not form a spindle. b. nimal cells lack cytokinesis. c. lant cells lack a cell plate. d. lant cells lack centrioles. 8. elect the incorrect association. a. 1 cell grows in size b. 2 protein synthesis occurs c. mitosis nuclear division d. fails to duplicate 9. he phase of cell division in which the nuclear envelope and nucleolus are disappearing as the spindle fibers are appearing is called a. anaphase. b. prophase. c. telophase. d. metaphase. 10. n animal cells, cytokinesis takes place by a. membrane fusion. b. a furrowing process. c. formation of a cell plate. d. cytoplasmic contraction. 11. f a cell is to divide, replication must occur during a. prophase. b. metaphase. c. anaphase. d. telophase. e. interphase. 12. f a cell had 18 chromosomes, how many chromosomes would each daughter cell have after mitosis? a. 9 b. 36 c. 18 d. cannot be determined 13. he cell cycle a. includes mitosis as an event. b. includes only the stages 1,, and 2. c. is under cellular, but not under genetic, control. d. involves proteins but not chromosomes. 14. When do chromosomes move to opposite poles? a. prophase b. metaphase c. anaphase d. telophase 15. Which of the following does describe the behavior of cells in a malignant tumor? a. carry out metastasis b. lose the ability of contact inhibition c. multiply rapidly d. remain in one site 16. Which of these might explain why vitamins and help prevent cancer? a. hey kill bacteria in the gut. b. hey are antioxidants. c. hey cause the growth of cells. d. hey kill cells. 17. Which of these is a characteristic of cancer cells? a. specialization of structure and function b. metastasis c. uncontrolled growth d. nondifferentiation 18. etastasis is a. involved in the initiation of cancer. b. a localized tumor. c. cured by the proper diet. d. the spread of cancerous cells. 69

mad17743_ch08.qxd 3/9/06 3:47 age 70 19. he formation of new blood vessels, as in a cancerous growth, is a. angiogenesis. b. spermatogenesis. c. oogenesis. d. metastasis. 20. hemotherapy following surgery is for the purpose of a. supplying the body with the chemicals it needs. b. catching stray cells that have or might metastasize. c. preventing resistance from occurring. d. curing leukemia only. Q he introduction to this chapter is about the importance of mitosis to the body, as demonstrated by the inability of nervous tissue to repair itself. 21. f you accidentally cut off the tip of your finger, the treatment very well could include the application of growth hormone. What would be the purpose of this treatment? 22. his demonstrates that the function of mitosis is. 23. rowth hormone and cyclin, which help regulate the cell cycle, are proteins. o you predict that genes control the synthesis of growth hormone and cyclin? Why or why not? 24. Based on experiments with rats, some scientists believe there are adult stem cells in the brain. f so, what might be a new treatment for lzheimer disease, based on your answer to question 21? est esults: number correct 24 = 100 = % X, the ssentials of Biology website: http://www.mhhe.com/maderessentials, the website for ssentials of Biology, offers access to a wide variety of tools to help students learn biological concepts and to reinforce their knowledge. nline study aids such as practice quizzes, interactive activities, animations, labeling exercises, flashcards, and much more are organized according to the major sections of each chapter. here is even an online tutorial service! W a. somatic cell b. cytokinesis c. centrosome d. cell cycle e. centromere f. tumor g. sister chromatid h. chromatin i. apoptosis j. cyclin k. interphase l. spindle daughter chromosomes. h. pindle disappears as new nuclear envelopes form. 6. a. cleavage furrowing b. anaphase and telophase 7. lant ell nimal ell X 1. a. b. c. d. 2. e, c, a, d, b 3. a. duplicated chromosome b. sister chromatids c. daughter chromosomes d. eight e. 4. a. aster b. centriole c. centromere d. spindle fiber e. centrosome f. nuclear membrane fragment g. chromosome 5. a. prophase b. metaphase c. anaphase d. telophase e. hromosomes are condensing. f. hromosomes are aligned at the spindle equator. g. ister chromatids separate becoming no no no 70

mad17743_ch08.qxd 3/9/06 3:47 age 71 8. a. es and they form a spindle. b. no c. t seems not, because plant cells have no centrioles, yet they have a spindle. 9. a. 1 checkpoint b. 2 checkpoint c. checkpoint 10. a. b. c. d. 11. a. nondifferentiated cells b. abnormal nuclei c. no contact inhibition d. disorganized, multilayered 12. a. one b. multiple c. contact d. tumor e. benign f. malignant g. metastasis 13. a. 2 b. 4 c. 3 d. 5 e. 1 14. a. on t sunbathe. b. on t smoke. c. at fruits and vegetables. 1. c 2. a 3. b 4. d 5. a 6. b 7. d 8. d 9. b 10. b 11. e 12. c 13. a 14. c 15. d 16. b 17. a 18. d 19. a 20. b 21. to stimulate the cells in the area to undergo mitosis 22. growth and repair of tissues 23. es, because genes specify the sequence of amino acids in a protein. 24. nject growth hormone into the brain. W a. mitosis b. cytokinesis c. interphase d. chromatin e. spindle f. prophase g. centromere h. telophase 71