The process of cell division occurs in a series of stages or phases!!! Mitosis The process of cell division occurs in a series of stages or phases!!!

Limited cell size (reason they must divide) DNA “overload” Instructions found in the nucleus are sufficient to meet all the cells’ needs Exchanging Materials & Messages All requirements must pass into the cell through the membrane and all wastes must pass out of the cell through the membrane Surface Area-to-Volume Ratio Want greater surface area compared to volume Volume increases faster than does the surface area as a cell gets larger

Cell division accounts for three essential life processes: Growth-happens because cells grow to a maximum size, then divide Repair-repairing tissues only happens because of cell division Repairing a tiny cut to regeneration of an arm on a sea star Reproduction- asexual and sexual reproduction are dependent on cell division Asexual, a whole new organism grows (mitosis) Sexual, specialized cell division leads to production of egg and sperm cells allowing this to occur (meiosis)

Cell Cycle G1 = cell growth S = (synthesis) DNA replication These three make up Interphase which is the longest part of the cell cycle G1 = cell growth S = (synthesis) DNA replication G2 =some growth, preparation for mitosis M = mitosis (not a part of interphase) Cytokinesis

Interphase (G1, S, G2) nucleolus DNA starts as chromatin (long threads), but then winds up into chromosomes (coils) AFTER the copy is made. Each chromosome and its copy (sister) are attached and called sister chromatids at the end of this phase. Area where the sister chromatids are joined.

Mitosis Cell Division Prophase Metaphase Anaphase Telophase

Prophase Centrioles appear and begin to move to opposite ends of the cell. Spindle fibers form between the centrioles. Nuclear membrane starts to disappear. Chromosomes condensed/nucleolus not visible. Centrioles Spindle fibers

Metaphase Chromatids (or pairs of chromosomes) attach to the spindle fibers. Centrioles are at poles. Line up in middle

Anaphase Chromatids separate and begin to be pulled to opposite ends of the cell.

Telophase Two new nuclei form Chromosomes just begin to unwind Cytoplasm pinches inward

Cytokinesis In animal cells, the cell membrane pinches inward to create two daughter cells – each with its own nucleus with identical chromosomes. In plant cells, a structure known as the cell plate forms midway between the divided nuclei

Mitosis in Actual cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. has centrioles centrosome Animal Cell at Interphase aster 20 µm duplicated chromosome 20 µm spindle pole 9 µm metaphase plate chromosomes at 20µm daughter chromosome 20µm cleavage furrow 16µm nuclear envelope fragments centromere kinetochore nucleolus MITOSIS chromatin condenses nucleolus disappears spindle fibers forming spindle fiber kinetochore kinetochore spindle fiber polar spindle fiber Metaphase Centromeres of duplicated chromosomes of fully formed spindle). Kinetochore spindle are aligned at the metaphase plate (center fibers attached to the sister chromatids come from opposite spindle poles. Telophase Daughter cells are forming as nuclear envelopes and nucleoli reappear. Chromosomes will become indistinct chromatin. Early Prophase Centrosomes have duplicated. Chromatin is condensing into chromosomes, and the nuclear envelope is fragmenting. Prophase duplicated chromosomes are visible. Nucleolus has disappeared, and Centrosomes begin moving apart, and spindle is in process of forming. Prophase duplicated chromosomes are visible. Nucleolus has disappeared, and Centrosomes begin moving apart, and spindle is in process of forming. Anaphase Sister chromatids part and become daughter chromosomes that move toward the spindle poles. In this way, each pole receives the same number and kinds of chromosomes as the parent cell. centrosome lacks centrioles Plant Cell at Interphase 25µm cell wall chromosomes 6.2µm spindle pole lacks centrioles and aster 20µm spindle fibers 6.2µm 6.2µm cell plate 6.6µm Animal cell(Early prophase, Prophase, Metaphase, Anaphase, Telophase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.; Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase, Metaphase, Anaphase): © R. Calentine/Visuals Unlimited; Plant cell(Telophase): © Jack M. Bostrack/Visuals Unlimited;

Cell Cycle Control Cells have very careful control over the cell cycle: To maintain quality of cells Uncontrolled growth is Cancer Three environmental factors that cause cancer are: cigarette smoke air and water pollution exposure to ultraviolet radiation from the sun AND TANNING BEDS!!!

The Cell Cycle Interphase S (growth and DNA replication) G1 checkpoint Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Interphase S (growth and DNA replication) G1 checkpoint Cell cycle main checkpoint. If DNA is damaged, apoptosis will occur. Otherwise, the cell is committed to divide when growth signals are present and nutrients are available. G1 G2 checkpoint Mitosis checkpoint. Mitosis will occur if DNA has replicated properly. Apoptosis will occur if the DNA is damaged and cannot be repaired. G2 (growth and final preparations for division) G1 (growth) G0 M G2 Cytokinesis elophase Prophase Anaphase Metaphase Late prophase T M M checkpoint Spindle assembly checkpoint. Mitosis will not continue if chromosomes are not properly aligned.

Apoptosis Programmed cell death Like the cell is committing suicide

Characteristics of Cancer Cells Lack differentiation Are nonspecialized Are immortal (can enter cell cycle repeatedly) Have abnormal nuclei May be enlarged May have abnormal number of chromosomes Extra copies of genes Form tumors Mitosis controlled by contact with neighboring cells – contact inhibition Cancer cells have lost contact inhibition

Characteristics of Cancer Cells Undergo metastasis Original tumor easily fragments New tumors appear in other organs Undergo angiogenesis Formation of new blood vessels Brings nutrient and oxygen to tumor

Progression of Cancer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. New mutations arise, and one cell (brown) has the ability to start a tumor. primary tumor lymphatic vessel blood vessel Cancer in situ. The tumor is at its place of origin. One cell (purple) mutates further. lymphatic vessel blood vessel Cancer cells now have the ability to invade lymphatic and blood vessels and travel throughout the body. New metastatic tumors are found some distance from the primary tumor.

Origins of Cancer: Oncogenes Mutations in DNA repair mechanisms Oncogenes Proto-oncogenes (when they are healthy) promote the cell cycle in various ways Tumor suppressor genes inhibit the cell cycle in various ways Both normally regulated in coordination with organism’s growth plan If either mutates, may lose control and become oncogene (either one).

Origins of Cancer: Telomerase Chromosomes normally have special material at each end called telomeres (end parts) These get shorter each cell division When they get very short The cell will no longer divide Almost like running out of division tickets Telomerase is an enzyme that adds telomeres Mutations in telomerase gene: Keeps adding new telomeres Allow cancer cells to continually divide Like counterfeit tickets

d: © Biophoto Associates/Photo Researchers, Inc. Causes of Cancer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Heredity Radiation sources growth factor growth factor Activates signaling proteins in a stimulatory pathway that extends to the nucleus. Viruses receptor protein Pesticides and herbicides oncogene P a. Influences that cause mutated proto-oncogenes (called oncogenes) and mutated tumor suppressor genes P activated protein signaling P protein signaling Stimulatory pathway phosphate gene product promotes cell cycle b. Effect of growth factor Inhibitory pathway gene product inhibits cell cycle proto-oncogene Codes for a growth factor, a receptor protein, or a signaling protein in a stimulatory pathway. If a proto-oncogene becomes an oncogene, the end result can be active cell division. c. Stimulatory pathway and inhibitory pathway tumor suppressor gene Codes for a signaling protein in an inhibitory pathway. If a tumor suppressor gene mutates, the end result can be active cell division. d. Cancerous skin cell 1,100X d: © Biophoto Associates/Photo Researchers, Inc.

Animation Cyclin- any gene involved in regulating the cell cycle. Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

Normal cells obey strict rules. Divide only when told. Die rather than misbehave. ~Dr. Andrew Murray Harvard University

If only students were like “normal cells”. ~Dr. Tracey Schneeman Streetsboro High School

Stem Cells ADULT STEM CELLS Many mammalian organs contain stem cells Retain the ability to divide Aren’t totally differentiated (specialized) bone marrow stem cells divide to produce various types of blood cells EMBRYONIC STEM CELLS Have the ability to become ANY type of cell Currently controversial

Therapeutic cloning to produce human tissues can begin with either adult stem cells or embryonic stem cells Embryonic stem cells can be used for reproductive cloning, the production of a new individual

Prokaryotic Cell Division Prokaryotic chromosome is a ring of DNA 1,000 X length of cell Replicated into two rings prior to division Replicate rings attach to plasma membrane Binary fission Splitting in two between the two replicate chromosomes Produces two daughter cells identical to original cell – Asexual Reproduction

Binary Fission of Prokaryotes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. chromosome 1. Attachment of chromosome to a special plasma membrane site indicates that this bacterium is about to divide. cell wall plasma membrane cytoplasm 2. The cell is preparing for binary fission by enlarging its cell wall, plasma membrane, and overall volume. 200 nm 3. DNA replication has produced two identical chromosomes. Cell wall and plasma mem- brane begin to grow inward. 200 nm 4. As the cell elongates, the chromosomes are pulled apart. Cytoplasm is being distributed evenly.. 5. New cell wall and plasma membrane has divided the daughter cells. 200 nm (All): © Stanley C. Holt/Biological Photo Service.

January 30, 2008 Do you think all cells continue to cycle through mitosis throughout the entire life of a person? Are there any cells that you think do? Name them. Are there any cells that you think do not? Name them. (4 points)