1. BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor From PowerPoint ® Lectures for Biology: Concepts & Connections CHAPTER 8 The Cellular Basis of Reproduction and Inheritance Modules 8.1 – 8.11

2. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 1. All living organisms are composed of one or more cells. (1958 Virchow) 2. Cells are the most basic unit for function and structure of all organisms. 3. All cells come from cells that already exist through cell division. Cellular division has several functions: –Cell division allows an embryo to develop into an adult –Cell division heals wounds when inflicted –It also ensures the continuity of life from one generation to the next through the production of sperm and egg 8.2 Cells arise only from preexisting cells The Cell Theory

3. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic cells divide asexually –These cells possess a single chromosome, containing genes. There may be additional plasmids in bacteria. –The chromosome is replicated –The cell then divides into two cells, a process called binary fission 8.3 Prokaryotes reproduce by binary fission Figure 8.3B Prokaryotic chromosomes

4. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.3A Binary fission of a prokaryotic cell Prokaryotic chromosome Plasma membrane Cell wall Duplication of chromosome and separation of copies Continued growth of the cell and movement of copies Division into two cells

5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings A eukaryotic cell has many more genes than a prokaryotic cell. (A bacteria may have 3000 genes while a human may have 50,000 to 100,000) –The genes are grouped into multiple chromosomes, found in the nucleus. –To accomplish cell division, the chromosomes must go through temporary alterations in their structure. Some EUKARYOTIC CELLS can reproduce both sexually and asexually Figure 8.4A

6. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chromosomes are made of a very long DNA molecule with thousands of genes. The DNA in one human cell is approximately 2 meters long. –Individual chromosomes are only visible during cell division when they become tightly coiled. –Chromosomes are packaged as chromatin. Chromatin is DNA and proteins. –What is the adaptive advantage of becoming tightly coiled when the cell divides?

7. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Before a cell starts dividing, the chromosomes are duplicated. This must occur so that each daughter cell gets the same amount of DNA as the cell it came from. –This process produces 2 sister chromatids which make up one chromosome. Centromere Sister chromatids Figure 8.4B

8. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings When the cell divides, the sister chromatids separate –Two daughter cells are produced –Each has a complete and identical set of chromosomes Centromere Sister chromatids Figure 8.4C Chromosome duplication Chromosome distribution to daughter cells

9. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The cell cycle consists of two major phases: –Interphase, where chromosomes duplicate and cell parts are made –The mitotic phase, when cell division occurs 8.5 The cell cycle multiplies cells Figure 8.5

10. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic cell division consists of two stages: –Mitosis –Cytokinesis –Let’s take a closer look. 8.6 Cell division is a continuum of dynamic changes

11. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings INTERPHASEPROPHASE Centrosomes (with centriole pairs) Chromatin NucleolusNuclear envelope Plasma membrane Early mitotic spindle Centrosome Chromosome, consisting of two sister chromatids Fragments of nuclear envelope Kinetochore Spindle microtubules Figure 8.6

12. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings METAPHASETELOPHASE AND CYTOKINESIS Metaphase plate SpindleDaughter chromosomes Cleavage furrow Nucleolus forming Nuclear envelope forming ANAPHASE Figure 8.6 (continued)

13. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In animals, cytokinesis occurs by cleavage –This process pinches the cell apart 8.7 Cytokinesis differs for plant and animal cells Figure 8.7A Cleavage furrow Contracting ring of microfilaments Daughter cells

14. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In plants, a membranous cell plate splits the cell in two Vesicles containing cell wall material Cell plate forming Figure 8.7B Cell plateDaughter cells Wall of parent cell Daughter nucleus Cell wallNew cell wall

15. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Motor proteins

16. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

17. Microtubule http://www.cytochemistry.net/Cell- biology/microtubule_structure.htmhttp://www.cytochemistry.net/Cell- biology/microtubule_structure.htm

18. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Most animal cells divide only when stimulated, and others not at all In laboratory cultures, most normal cells divide only when attached to a surface –They are anchorage dependent. 8.8 Anchorage, cell density, and chemical growth factors affect cell division

19. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cells continue dividing until they touch one another –This is called density-dependent inhibition Cells anchor to dish surface and divide. Figure 8.8A When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (density-dependent inhibition).

20. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Growth factors are proteins secreted by cells that stimulate other cells to divide After forming a single layer, cells have stopped dividing. Figure 8.8B Providing an additional supply of growth factors stimulates further cell division.

21. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Proteins within the cell control the cell cycle –Signals affecting critical checkpoints determine whether the cell will go through a complete cycle and divide 8.9 Growth factors signal the cell cycle control system G 1 checkpoint M checkpoint G 2 checkpoint Control system Figure 8.9A

22. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The binding of growth factors to specific receptors on the plasma membrane is usually necessary for cell division Growth factor Figure 8.8B Cell cycle control system Plasma membrane Receptor protein Signal transduction pathway G 1 checkpoint Relay proteins

23. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cancer cells have abnormal cell cycles –They divide excessively and can form abnormal masses called tumors Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division 8.10 Connection: Growing out of control, cancer cells produce malignant tumors

24. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Malignant tumors can invade other tissues and may kill the organism Tumor Figure 8.10 Glandular tissue 123 A tumor grows from a single cancer cell. Cancer cells invade neighboring tissue. Lymph vessels Cancer cells spread through lymph and blood vessels to other parts of the body. Metastasis

25. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings When the cell cycle operates normally, mitotic cell division functions in: –Growth (seen here in an onion root) 8.11 Review of the functions of mitosis: Growth, cell replacement, and asexual reproduction Figure 8.11A

26. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cell replacement (seen here in skin) Dead cells Figure 8.11B Dividing cells Epidermis, the outer layer of the skin Dermis

27. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Asexual reproduction (seen here in a hydra) Figure 8.11C