Section 10-1: Cell Reproduction

1. Section 10-1: Cell Reproduction • Why do cells reproduce? • To help organisms grow and to replace old or damaged cell • Regeneration is the replacement of a lost or amputated body part (ex. Lizard tails, starfish arms)

2. Some cells are replaced frequently throughout an organism’s lifetime, however brain and nerve cells are rarely produced after infancy

3. All cell activity is regulated by the nucleus • Inside the nucleus, DNA is organized into hereditary units called genes. • A gene is a segment of DNA that codes for RNA and protein. • Because DNA is a very large molecule, it is organized and packaged into structures called chromosomes.

5. Prokaryotic chromosomes vs. eukaryotic chromosomes • A prokaryotic cell has a single, tangled loop of DNA that contains thousands of genes • Eukaryotic cells contain more genes that are arranged on several linear DNA molecules. (There are 46 chromosomes in human cells) • Normally, the DNA and proteins in a cell are in the form of chromatin

6. A fully condensed, duplicated chromosome has two thick strands called chromatids which are held together by a centromere. • During cell division, the sister chromatidsseparate at the centromere to ensure each new cell contains a copy of the parent cell

8. From the cell theory, we know that all new cells are produced by the division of pre-existing cells. • All newly formed cells require DNA, so before a cell can divide, a copy of DNA is made for each new daughter cell in the process of DNA replication.

9. In prokaryotic cells, the single circular chromosome divides, the cell grows in size, and a new cell wall forms in the middle of the cell and pinches off into two independent daughter cells. • In eukaryotic cells, cell reproduction is more complex

10. Section 10-2: Mitosis From page 230

11. Cell cycleis a repeating sequence of cellular growth, DNA replication, and division during the life of a cell • Made up of 5 phases (3 of which are known as interphase)

12. Preparing for cell division • Interphase: Cell is growing and preparing to divide • G1: (first gap phase) cell grows rapidly for the cell to build more organelles; most of cell’s life spent here • G1 checkpoint before moving on to S phase • The cell must be large enough • Cell needs enough nutrition • The cell will enter a resting period if the checkpoint is not passed

13. More interphase… • S: (synthesis phase) cell’s DNA is copied; nucleus contains two complete sets of DNA • G2: (second gap phase) cell continues to grow and prepares to divide; microtubules organize in cytoplasm in preparation to divide • G2 checkpoint: Ensures the DNA of the daughter cells will be identical to the parent cell’s DNA, DNA is undamaged, and that the cell is large enough to undergo division

14. Cell division (included mitosis and cytokinesis) • Process of dividing the nucleus into two is called mitosis • Process of separating the organelles and cytoplasm is called cytokinesis

15. Mitosis consists of four stages: prophase, metaphase, anaphase, telophase • refer to page 230 for more detailed descriptions

17. Prophase • Nuclear membrane breaks down • Centrioles moves to opposite poles and the spindle forms Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

18. Prophase

19. Metaphase • Chromosomes line up along the equator • Spindle fibers link to each chromatid Section 10-2 Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming Go to Section:

20. Metaphase

21. Anaphase • Spindle fibers shorten and pull chromatids to opposites poles of the cell Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

22. Anaphase

23. Telophase • A new nuclear envelope forms at each pole • The spindle dissolves • Chromosome uncoil • Cytokinesis begins Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

24. Telophase

25. Cytokinesis • The cell membrane grows into the center of the cell and divides it into two daughter cells of equal size. Each daughter cell has about half of the parent’s cytoplasm and organelles. • In animal cells, a belt of protein threads pinch off the cell in half • In cells with rigid cell walls, vesicles holding cell wall material line up across the middle of the cell and fuse to form a large membrane-bound cell wall called the cell plate

26. Cytokinesis Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

27. Cytokinesis