1. THE CELL CYCLE Chapter 12

2. Why is this relevant for you? Just in the past second, millions of your cells have divided in two. You began life as a single cell, but there are now more cells in your body than stars in the Milky Way. The dance of the chromosomes in a dividing cell is so precise that only one error occurs in 100,000 cell divisions. Half of all Americans will develop cancer during their lifetime.

3. Multicellular diploid adults (2n  46) MEIOSIS FERTILIZATION MITOSIS 2n2n and development Key Sperm cell n n Diploid zygote (2n  46) Diploid (2n) Haploid (n) Egg cell Haploid gametes (n  23) Figure 8.12

4. Distribution of Chromosomes During Eukaryotic Cell Division In preparation for cell division, DNA is replicated and the chromosomes condense Each duplicated chromosome has two sister chromatids (joined copies of the original chromosome), which separate during cell division The centromere is the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached 0.5  m Centromere Sister chromatids

5. Chromosomes Chromosomal DNA molecules Centromere Chromosome arm Chromosome duplication (including DNA replication) and condensation Sister chromatids Separation of sister chromatids into two chromosomes 1 2 3

6. Duplicated chromosomes (sister chromatids) TEM Tight helical fiber Looped domains Centromere Figure 8.4b

7. TEM Nucleosome “Beads on a string” Histones DNA double helix Figure 8.4a

8. Time (Hours) Number of Cells Stage 01 0.52 464 610,000 1030,000 1101 million This table represents the rate of cell division for the fertilized egg of an African frog (Xenopus). If each of the early divisions occurs at the same time, how many divisions take place in the first four hours? 1.3 divisions 2.4 divisions 3.5 divisions 4.6 divisions

9. Cell Cycle, Mitosis and Meiosis We’ll do the quiz together http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__control_of_the_cell_cycle.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__control_of_the_cell_cycle.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__how_the_cell_cycle_works.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__how_the_cell_cycle_works.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__mitosis_and_cytokinesis.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__mitosis_and_cytokinesis.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__comparison_of_meiosis_and_mitosis__quiz_1_.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter2/animati on__comparison_of_meiosis_and_mitosis__quiz_1_.html

10. Examine the micrograph of a growing onion root tip. The circled cells are in various stages of the cell cycle—most are in the mitotic phase. Which of the lists below correctly identifies the mitotic phases for the circled cells? a.b. c.d. 1. interphaseprophaseprophaseprophase 2. prophasetelophaseinterphaseinterphase 3. metaphasemetaphaseanaphasemetaphase 4. anaphaseanaphasetelophasetelophase 5. telophaseinterphasemetaphaseanaphase d. prophase interphase metaphase telophase anaphase

11. Cytokinesis: A Closer Look In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow In plant cells, a cell plate forms during cytokinesis (a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (TEM) Cleavage furrow Contractile ring of microfilaments Daughter cells Vesicles forming cell plate Wall of parent cell Cell plate New cell wall Daughter cells 100  m 1  m

12. 1 Origin of replication E. coli cell Two copies of origin Cell wall Plasma membrane Bacterial chromosome Origin Chromosome replication begins. Replication continues. Replication finishes. Two daughter cells result. 2 3 4

13. Figure 12.19 Anchorage dependence Density-dependent inhibition (a) Normal mammalian cells (b) Cancer cells 20  m

14. One of the first human cell lines to survive indefinitely was derived from a cancer patient who died in 1951. Known as the HeLa line for Henrietta Lacks, the cell line continues today in laboratories throughout the world and is even available for high school classrooms to study karyotyping. In 1951 people didn’t fully realize the potential applications of unique cells or DNA. Do you think that a patient should retain all rights to his or her cells or DNA during medical procedures? Strongly Agree Strongly Disagree A. E. C. B. D.

15. A normal cell is converted to a cancerous cell by a process called transformation Cancer cells that are not eliminated by the immune system, form tumors, masses of abnormal cells within otherwise normal tissue If abnormal cells remain at the original site, the lump is called a benign tumor Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form additional tumors

16. Figure 12.20 Glandular tissue Tumor Lymph vessel Blood vessel Cancer cell Metastatic tumor A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue. Cancer cells spread through lymph and blood vessels to other parts of the body. Cancer cells may survive and establish a new tumor in another part of the body. 4321

17. These are two mammograms—the one on the left is normal and the one on the right indicates a tumor. Genetic tests are now available to screen for women with a high genetic risk for developing breast cancer. Some women in this situation have opted for a radical mastectomy before the appearance of a tumor. As a doctor, would you consider advising your patient in this manner? Strongly Agree Strongly Disagree A. E. C. B. D.

18. Pair of homologous chromosomes LM One duplicated chromosome Centromere Sister chromatids HUMAN KARYOTYPE