1. Biology Chapter 10: Cell Growth and Division * This presentation contains copyrighted material.

2. Let's start from the beginning... A long time ago our ancestors noticed that some things tended to reproduce themselves - traits were inherited. Unfortunately, that's not always a good thing!

3. What is a chromosome? Threadlike structure in nucleus > contains genetic information - passed on from one generation of cells to the next –Genetic information = DNA (“blueprints” of life) –DNA in form of a code (genes) > dictates everything from eye color to how long you live –“It’s in your genes” should actually be “It’s in your DNA

4. Gene Sequence of DNA that codes for a protein and determines a trait –Trait = specific characteristic that varies from one individual to another –Ex: height, hair and eye color Genes are the bands on chromosomes. –The thicker the band, the more information it holds.

7. Living things grow by producing cells. bacteria (0.5 to 1.5 microns) red blood cell (5 microns) lymphocyte (5 to 8 microns)

8. As a cell grows larger, it… Places more demands on its DNA –DNA “Overload” –Compare to town library (town grows, more demand for books) Has more trouble moving enough nutrients and wastes across its membrane (in and out of cell)

9. The cell will eventually divide into two daughter cells.

11. Cell Division Process by which a cell divides into two daughter cells –DNA replicated before division –Each daughter cell gets one complete set of genetic information Two stages: –Mitosis - nucleus divides to form two identical nuclei –Cytokinesis - cytoplasm divides to form two identical cells

12. Chromosomes Made up of DNA (genetic information) and proteins > chromatin Each chromosome has two identical “sister” chromatids - one goes to each new cell Cells of every organism have specific number of chromosomes –Ex: fruit flies 8, carrots 18, humans 46

13. Duplicated chromosomes are called dyads Duplicates held together by centromere Homologous pair = 1 of each pair acquired from one of the parents

15. The Cell Cycle Cell grows, replicates its DNA, and divides into two daughter cells Four phases ~M phase > Mitosis and cytokinesis (cell division) ~S phase > Synthesis (chromosome replication) ~G 1 and G 2 > “Gap” phases (periods of intense Growth and activity)

17. Interphase Period of cell cycle between cell divisions All phases except M –Made up of G 1, S, and G 2 phases –Split because M phase occurs much more quickly Includes: DNA replication, protein synthesis, and synthesis of organelles and materials needed for cell division

19. Mitosis > Process in which the nucleus divides to form two identical nuclei

20. Four Phases of Mitosis Prophase Metaphase Anaphase Telophase

21. Prophase Chromatin condenses into chromosomes Nucleolus disappears Centrioles separate –Two tiny “anchors” in cytoplasm near nuclear envelope Fanlike fibers extend to form spindle

22. Pair of Centrioles Centromere Chromosome (two sister chromatids)

23. Metaphase Chromosomes line up along center of cell –Each chromosome connected to spindle at centromere

24. (Imaginary line )

25. Anaphase Sister chromatids separate and move to opposite sides of cell

27. Telophase Chromosomes gather at opposite ends of cell Two new nuclear envelopes form

28. Chromosomes gathering New nuclear envelopes forming

29. Cytokinesis Cytoplasm pinches in half Each daughter cell has identical set of duplicate chromosomes

31. New individual cell

32. Uncontrolled Cell Growth Cancer –Disorder in which some cells lose ability to control growth –Cells do not respond to signals that regulate growth of most cells –Result > divide uncontrollably and form masses of cells called tumors

33. Results of Mitosis Mitosis is the division of a NUCLEUS Mitosis produces two new nuclei with the SAME number of chromosomes as original nucleus Mitosis is ASEXUAL –ONE parent = 2 IDENTICAL daughters