2. Cell division All complex organisms originated from a single fertilized egg. Every cell in your body started here, through cell division the numbers are increased ** 100 trillion cells in body came from one cell! Why do cells have to divide?? 1.They can only grow so big to support themselves 2.Cell in a multicellular organism specialize and change into their various roles www.worldofteaching.com

3. So before we talk about cell division, there are a few things to understand that won’t be covered until later chapters… 1. What is DNA? 2. How are DNA & chromosomes related?

4. More about chromosomes… http://www.youtube.com/watch?v=XQ5BgosJHek

5. You will often see chromosomes drawn like this: usually chromosomes are single stranded unless they have to duplicate genetic material before dividing duplicated chromosomes are usually drawn to look more like an “X” OR

6. So for humans: We have 46 chromosomes, or 23 pairs – half from mom & half from dad We could line up all of our chromosomes from largest to smallest & there would always be a match for mom to dad – each pair carrying the information for the same trait Except the last pair – the sex chromosomes: girls = XX & boys = XY

7. 6 Functions of Cell Division 20 µm 100 µm 200 µm (a) Reproduction. An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism (LM). (b) Growth and development. This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming two cells (LM). (c) Tissue renewal. These dividing bone marrow cells (arrow) will give rise to new blood cells (LM). www.austincc.edu/rfofi/BIO1308/BIO1308ppt/Bio1308Mitosis.ppt binary fission mitosis division of somatic (body) cells (autosomes) meiosis division of gametes (sex cells) ASEXUAL REPROCUTION SEXUAL REPROCUTION

8. More about cell division… http://www.youtube.com/watch?v=11STwx1Fv_g

9. 8 Cell Division An integral part of the cell cycle Results in genetically identical daughter cells Cells duplicate their genetic material – Before they divide, ensuring that each daughter cell receives an exact copy of the genetic material, DNA www.austincc.edu/rfofi/BIO1308/BIO1308ppt/Bio1308Mitosis.ppt

10. 9 DNA Genetic information - genome Packaged into chromosomes 50 µm Figure 12.3 www.austincc.edu/rfofi/BIO1308/BIO1308ppt/Bio1308Mitosis.ppt

11. 10 DNA And Chromosomes An average eukaryotic cell has about 1,000 times more DNA then an average prokaryotic cell. The DNA in a eukaryotic cell is organized into several linear chromosomes, whose organization is much more complex than the single, circular DNA molecule in a prokaryotic cell www.austincc.edu/rfofi/BIO1308/BIO1308ppt/Bio1308Mitosis.ppt

12. 11 Chromosomes All eukaryotic cells store genetic information in chromosomes. – Most eukaryotes have between 10 and 50 chromosomes in their body cells. – Human cells have 46 chromosomes. – 23 nearly-identical pairs www.austincc.edu/rfofi/BIO1308/BIO1308ppt/Bio1308Mitosis.ppt

13. Cell Reproduction REMEMBER:  Prokaryotes: bacteria  Eukaryotes: plants,animals, protists & fungi copyright cmassengale

14. Prokaryotes  Lack a nucleus  Have a single chromosome  Reproduce by binary fission  Include bacteria copyright cmassengale

15. Steps in Binary Fission  Used by bacteria  Cells increase their cell mass slightly  DNA & cell components are replicated  Each cell divides into 2 daughter cells copyright cmassengale

16. Binary Fission of Bacterial Cell copyright cmassengale

17. E. Coli Dividing by Binary Fission copyright cmassengale

18. More on binary fission… http://www.youtube.com/watch?v=hOyUcjqcGpQ

19. Eukaryotes  Contain a nucleus & membrane bound organelles  Asexually reproduce cells by mitosis  Sexually reproduce by meiosis copyright cmassengale

20. Mitosis and Meiosis Mitosis: -division of somatic (body) cells (also called autosomes) Meiosis -division of gametes (sex cells): produces haploid cells (cells with half the normal number of chromosomes – so it can join with another to make a complete number – will discuss later...

21. Mitosis & the Cell Cycle Function: growth, repair, and replacement of cells. A diploid parent cell (cell with complete set of chromosomes, half from mom & half from dad) replicates its DNA, then splits in half. Both new daughter cells have a complete set of DNA Kim Brown

22. 21 Phases of the Cell Cycle The cell cycle consists of – Interphase – normal cell activity – The mitotic phase – cell divsion INTERPHASE Growth G 1 (DNA synthesis) Growth G 2 Cell Divsion www.austincc.edu/rfofi/BIO1308/BIO1308ppt/Bio1308Mitosis.ppt

23. Three Stages of the Cell Cycle The cell cycle has 3 stages: Interphase: growth and replication Mitosis: the nucleus divides Cytokinesis: the cell divides The cell cycle has 3 stages: Interphase: growth and replication Mitosis: the nucleus divides Cytokinesis: the cell divides Kim Brown

24. Cell Cycle: An Interactive Animation

25. End Show 10-2 Cell Division Slide 24 of 38 Copyright Pearson Prentice Hall The Cell Cycle The cell cycle consists of four phases: G 1 (First Gap Phase) S Phase G 2 (Second Gap Phase) M Phase (cell division) Mitosis (Prophase, Metaphase, Anaphase, Telophase) Cytokinesis INTERPHASE

26. End Show 10-2 Cell Division Slide 25 of 38 Copyright Pearson Prentice Hall Cell Cycle Events of the Cell Cycle

27. End Show 10-2 Cell Division Slide 26 of 38 Copyright Pearson Prentice Hall Events of the Cell Cycle During G 1, the cell increases in size synthesizes new proteins and organelles During the S phase, chromosomes are replicated DNA synthesis takes place Once a cell enters the S phase, it usually completes the rest of the cell cycle. The G 2 Phase (Second Gap Phase) organelles and molecules required for cell division are produced Once G 2 is complete, the cell is ready to start the M phase—Mitosis

28. Cell Cycle  Stages in growth & division  G1 Phase  S Phase  G2 Phase  M Phase  Cytokinesis copyright cmassengale Review:

29. G1 Phase  First growth stage  Cell increases in size  Cell prepares to copy its DNA copyright cmassengale

30. Synthesis Phase  Copying of all of DNA’s instructions  Chromosomes duplicated copyright cmassengale

31. G2 Phase  Time between DNA synthesis & mitosis  Cell continues growing  Needed proteins produced copyright cmassengale

32. M Phase  Cell growth & protein production stop  Cell’s energy used to make 2 daughter cells  Called mitosis or karyokinesis (nuclear division) copyright cmassengale