Cell Growth and Reproduction

1. Cell Growth and Reproduction Cell Size Mitosis Meiosis

2. Growth in Organisms For an organism to grow, its cells divide instead of getting larger.

3. Cell Size Limitations 1 • Large cells would have to wait too long to diffuse nutrients in and waste out. • Ex. a/c

4. Cell Size Limitations 2 • One set of DNA can’t make enough proteins and enzymes fast enough for a large cell. • Ex. Only one cook

5. 4mm 2mm 4mm 1mm 1mm 2mm 4mm 1mm 2mm Surface area =6mm2 Surface area= 24mm2 Surface area= 96mm2 Volume= 1mm3 Volume = 8mm3 Volume= 64mm3 12:2 ratio 6:2 ratio 3:2 ratio Cell Size Limitations 3 • Surface area-to-volume ratio: • The volume (inside) of the cell increases a lot faster than the surface area (membrane). • Ex. Solar panels

6. Cell Cycle • Cell cycle – stages of growth, preparation, and division (Interphase and Mitosis)

7. Interphase • Interphase- period of normal growth and maintenance. (3 stages) • G1=growth • Synthesis=copy chromosomes • G2= maintenance.

8. DNA • chromosome – packaged DNA (like DNA suitcases) • Each cell has 46 chromosomes (23 from mom and 23 from dad). • Diploid – a cell with 2 set of chromosomes. (somatic cells)

9. Mitosis • 1 diploid parent cell splits into 2 identical diploid daughter cells. • Copied chromosomes made in synthesis are called sister chromatids… held together by centromeres. chromosomes Parent cell Sister chromatids identical daughter cells

10. Prophase • Nuclear envelope disappears, sister chromatids unpack • Centrioles (dark cylinders) form at opposite ends of the cell • Spindle fibers grow out of cenrioles.

11. Metaphase • spindle fibers attach to each of the sister chromatids and line them up in the center of the cell.

12. Anaphase • spindle fibers pull the sister chromatids apart at the centromere. • Each side gets a copy of the chromosomes.

13. Telophase • chromosomes are on opposite sides of the cell • spindle fibers disappear • the nuclear envelope reforms • cytokinesis - The cytoplasm is pinched down the middle by a cleavage furrow.(split by a cell plate in plants)

14. Mitosis Vid Mitosis

15. Why mitosis? • Somatic cells divide for growth or maintenance. • What about reproduction?

16. Meiosis • 1 diploid parent cell divides twice into 4 haploid unidentical daughter cells • Haploid – 1 set of chromosomes. • meiosis forms sperm or eggs called gametes . (gametes are haploid…1 set of 23 chromosomes)

17. Prophase I • Homologous Chromosomes- a pair of chromosomes that have genes for the same trait (one from mom, one from dad) • During prophase I, Tetrads form. A tetrad is two homologous chromosomes made of sister chromatids linked together. Homologous chromosomes Sister chromatids tetrad

18. Crossing over • These tetrads will trade genetic information in a process called crossing over. (new gene combinations form)

19. Metaphase I • During metaphase I tetrads are lined up at the equator of the cell. • Independent assortment- mom and dad’s chromosomes line up in any order.

20. Anaphase I, Telophase 1 • During anaphase I, the tetrads are split into chromatids and pulled to opposite sides of the cell. • During telophase I the cell is split into two diploid cells.

21. Meiosis II • 2nd Stage Meiosis II (P II, M II, A II, T II) • Prophase, metaphase, anaphase, telophase are repeated just like mitosis to split the chromatids into chromosomes.

22. Why go through the Trouble? • Each parent produces new combinations of genes through crossing over, independent assortment and random fertilization.

23. Cancer • Cancer is when cells divide uncontrollably. They usually stop dividing when they touch other cells.