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The Cell Cycle

Explore the process of cell division and the different stages of the cell cycle. Learn about chromosomes, DNA packaging, and the importance of mitosis. Discover how cells grow, develop, and heal through the cell cycle.

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The Cell Cycle

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  1. The Cell Cycle

  2. How do cells divide? Cell division is a pattern of growth and division for the cell. The cell will grow so that when it divides it will be the proper size and the new cell will have all of the “parts” that it needs. Cells will continue to do this until they die.......

  3. The cell cycle focuses on what happens in the nucleus……. So lets first get to know the terms associated with our DNA.

  4. Every cell has 6 feet of DNA inside its nucleus! How much DNA is that?

  5. How does the cell fit 6 ft of DNA in a nucleus? • The DNA is tightly packaged inside the nucleus. • We will see how this works on the next slide.

  6. Chromatin: • DNA and proteins spread out loosely in the nucleus • Like a bowl of spaghetti

  7. Chromosome: Long, rod-shaped structures composed tightly wound chromatin Duplicated Chromosome: Even when it is duplicated it is still considered a chromosome… …just duplicated Each arm is now called a sister chromatid held together at the centromere *ONLY IN THIS STAGE WHEN THE CELL IS DIVIDING!

  8. Chromosome Structure Sister chromatids centromere chromatin

  9. Chromosomes are formed from a single DNA strand that contains MANY genes • NOTE: Gene = a region of DNA that controls a hereditary characteristic (trait)

  10. 1 chromosome = 1-strand of DNA How many strands of DNA do we have in a normal body cell? 46 Click for size perspective

  11. Chromosomes Numbers • Every species has a set number of chromosomes in each cell • Humans have 46 chromosomes (23 pairs) in EVERY cell with the EXCEPTION of sex cells

  12. Do you think that the number of chromosomes indicates how highly developed an organism is? Check out other organisms!

  13. SEX CHROMOSOMES • chromosomes that determine the sex of an organism • For humans, Normal Female = XX Normal Male = XY • Chromosome pair #23 • AUTOSOMES • All of the other chromosomes in an organism. • Chromosome pairs #ed 1-22

  14. Organisms receive one copy of each autosome and one of the sex chromosome from each parent • So we have 23 pairs! • One from mom and one from Dad • The two copies of each autosome are called HOMOLOGOUS CHROMOSOMES • Their “bands” line up!

  15. HOMOLOGOUS CHROMOSOMES = chromosomes of the same size, shape, and banding pattern. One chromosome of the pair came from each parent. Their “bands” line up!

  16. Haploid (1n) =cells that contain only ONE SET of chromosomes (germ cells/sex cells/gametes) Diploid (2n)= cells that contain TWO SETS of chromosomes (somatic cells / body cells)

  17. When a sperm cell (1n) and an egg cell (1n) combine, the new cell will be diploid (2n)

  18. Karyotype: • A picture of the chromosomes in a dividing cell • Used to examine an individual’s chromosomes

  19. KARYOTYPE Normal Male

  20. Karyotype Karyotype BEFORE Mitosis http://wise.berkeley.edu/student/topFrame.php?projectID=23132 Karyotype AFTER Mitosis http://wise.berkeley.edu/student/topFrame.php?projectID=23132

  21. Haploid cell Diploid cell http://scigjt13.wordpress.com/2011/03/02/karyotype-of-alzheimers-disease/

  22. Remember: How many chromosomes do humans have?

  23. The Cell Cycle: Interphase and Mitosis Mitosis is a process that helps organisms grow, develop, and heal. Mitosis refers to the division of “body cells.” Think My Toe

  24. 2 main parts to the cell cycle 1. Interphase 2. Cell Division (AKA--Mitotic Phase)

  25. 1. Cell Cycle: Interphase 3-phases

  26. INTERPHASE: • Period of cell growth and development that precedes mitosis and follows CYTOKINESIS (cell splitting) • Longest phase of the cell cycle Centrioles

  27. 3-stages of interphase • G1 = Growth 1—most cell growth (cell contents are duplicated) • S = Synthesis—DNA is duplicated • G2 = Growth 2: cell grow a little to prepare for division, organelles double and cell “double checks” for errors

  28. 2. Cell Cycle: Cell Division (mitosis plus cytokinesis) 4-phases

  29. 1. PROPHASE: • Chromatin condense and thicken, now called chromosome. (DUPLICATED) • Nuclear envelope breaks down • Centrioles move to opposite "poles“ (or ends) of the cell

  30. 2. METAPHASE: • The spindle fibers (centriole) fully develops • The duplicated chromosomes align at the metaphase plate (middle)

  31. 3. ANAPHASE: • Sister chromatids of the duplicated chromosomes separate and begin moving to opposite ends (poles) of the cell. • Spindle fibers lengthen and elongate the cell. • Each pole contains a complete set of chromosomes.

  32. 4. TELOPHASE: • Nucleus begins to form at opposite poles. • The nuclear envelopes and nucleoli also reappear.

  33. Last event: Cytokinesis

  34. CYTOKINESIS: = the division of the original cell's cytoplasm. (There are now two separate cells)

  35. Cytokinesis: Animal Cell vs. Plant cell Animal Cell • Cleavage furrow forms and pinches cell in half. http://wps.aw.com/bc_campbell_concepts_5/30/7910/2025031.cw/index.html

  36. Cytokinesis: Animal Cell vs. Plant cell Plant Cell • Cell plate forms to divide the cell. http://wps.aw.com/bc_campbell_concepts_5/30/7910/2025031.cw/index.html

  37. MITOSIS CELL CYCLE • Interphase • Cell Division (Mitosis + Cytokinesis) • Prophase • Metaphase • Anaphase • Telophase

  38. Overview of the Cell Cycle

  39. Cell Cycle Regulation • Cell growth and division are carefully controlled. • Not all cells will go through the cell cycle at the same rate. • Examples of cells • rapidly dividing: • Examples of cells NOT dividing often: RBC Skin cells Muscle cells Nerve cells Bone marrow http://stearn.ca/blog/wp-content/uploads /2009/05/red-blood-cells.bmp http://www.caring4cancer.com/uploadedImages/Website-C4C-20/Skin _Cancer_(Non-Meloma)/The_Basics/Epidermis-dermis.jpg Digestive tract cells http://apps.uwhealth.org/adam/graphics/images/en/19917.jpg http://activebodyreadymind.com/images/Nerve.jpg http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book= cooper&part=A1967&rendertype=figure&id=A1982 http://www.rush.edu/rumc/images/ei_0062.gif

  40. Cell Cycle Regulation continued . . . • Cells that do not need to grow and divide can • enter G0 (resting) until they are needed.

  41. Regulation • Cells have both internal and external regulators. • Internal regulators: called cyclins, they make sure the cell is ready at certain checkpoints… • If not, the cycle stops (see diagram) Are all of the chromosomes attached to spindle fibers and properly aligned on the metaphase plate? Is the cell big enough? Has all of the DNA duplicated completely or properly? Is the cell big enough?

  42. Regulation continued . . . External regulators are called growth factors. Contact inhibition: cells won’t divide when they are touching other cells Anchorage Dependence: cells won’t divide if they are not on a stable surface. Density-dependent inhibition http://media.pearsoncmg.com/bc/bc_campbell_concepts_5/media/art/ch8/ir/imagelib_tab_1/33.htm

  43. What happens if cells LOSE the • ability to CONTROL the cell cycle? Cancer http://www.yourcancertoday.com/ContentResources/Image/growth.jpg

  44. Cancer • Cancer = uncontrolled cell growth • . . . cancer cells do NOT respond to regulator signals • . . . results in masses of cells called tumors • . . . cancer = a disease of the cell cycle http://www.youtube.com/watch?v=LEpTTolebqo&feature=related

  45. 2014 Cancer Statistics Source: American Cancer Society

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