1. Anatomy of a Chromosome Centromere - point where sister chromatids are joined together P=short arm; upward Q=long arm; downward Telomere-tips of chromosome p -arm centromere q-arm telomerechromatids

2. How is a karyotype prepared? - The resulting cells are placed in a solution that causes the cell membranes to rupture. - The chromosomes are stained and photographed. - The chromosomes may then be cut out of the photograph and arranged by homologous pairs. - A sample of cells is allowed to reproduce - A chemical called colchicine is added to stop the cell division during metaphase. http://www.mwit.ac.th/~bio/assets/karyotype_m utation.swf

3. What are homologous chromosomes? -matching pairs of chromosomes -similar in size and carrying information for the same genes -They are not identical (i.e. non-sister chromatids) -Sex chromosome XY pair is NOT a homologous pair as Y is too short -Non-sex chromosomes are called autosomes

4. Asexual Reproduction and Mitosis

5. Asexual Reproduction –New individual is produced from a single parent by cell division (i.e. without the use of sex cells) Female aphids give birth to genetically identical female offsprings Hydra asexually reproduce by budding Strawberry runners - Offsprings are genetically identical to one another and to the parent

6. Asexual reproduction Parent organism does not have to seek out mate No specialized mating behaviours nor anatomy required AdvantagesDisadvantages Low or no genetic diversity Entire population of identical offspring can be wiped out in case of environmental changes (e.g. diseases, competitor, volcanic eruptions etc.)

7. The cell cycle Most of the cells life is spent in Interphase –Obtaining energy –Synthesizing products –Repairing damage G1 - Rapid Growth S - DNA Synthesis & Replication G2 - Centrioles replicate in preparation for cell division

8. Interphase = G1 growth phase + G2 growth phase and S phase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

9. Mitosis Overview

10. Mitosis (mitos = “thread” in Greek) - A process that ensures genetically identical cells - Only occurs in eukaryotic, somatic cells (i.e. non-sex cells) -Before cell division, cells MUST undergo DNA replication - This creates 2 complete sets of DNA; one set for each cell after the division

11. MITOSIS Occur in both plant and animal cells Has 4 stages 1.Prophase (Beginning phase) 2.Metaphase (Middle phase) 3.Anaphase (second last phase) 4.Telophase (last phase) Thus, PMAT for short NOTE: Interphase is not a phase of mitosis, it’s a phase in cell cycle. However, it is usually mentioned in mitosis (thus, IPMAT)

12. Prophase of mitosis Nuclear membrane fades Chromosomes condense – can see sister chromatids and centromere Spindle fibre forms Centrioles start to move to opposite poles Animal Cell Plant Cell Spindle fibers

13. Metaphase of mitosis - Chromosomes line up at the equatorial plate (middle) of the cell - Each chromatid is attached to spindle fibres at centromere Animal Cell Plant Cell

14. Anaphase of mitosis -Proteins that hold pair of chromosomes at centromere break apart - Spindle fibres has been stretched like an elastic band now pulling a chromatid (one chromosome of a pair) toward each end of the cell Animal Cell Plant Cell

15. Telophase of mitosis - Spindle fibres dissolve - Nuclear membrane reforms around chromosomes of the 2 new nuclei - Chromosomes relax into chromatins Animal Cell Plant Cell

16. Cytokinesis -The nucleus has now been copied - Cell next undergoes cytokinesis: - Cytoplasm and organelles are copied before telophase completes - Proteins around middle of the cell starts to contract, pinching the cell membrane inward - Create 2 daughter cells -Cytokinesis completes cell division - Cell then enter into its resting phase: interphase (G1, S and G2)

17. Cytokinesis in plant cell - Rigid cell wall, can’t pinch membrane the way animal cell does - Instead: small vesicles (produced by Golgi body) line up between 2 new nuclei forming a cell plate - Cell plate grows outward and reaches the old cell wall - New cell membrane is formed

18. Result of mitosis -A parent cell becomes 2 new, genetically identical daughter cells -Each cell has the same set of chromosomes as the parent cells -WATCH THIS VIDEO: Recap of mitosis http://www.youtube.com/watch?v=VGV3fv- uZYI http://www.youtube.com/watch?v=VGV3fv- uZYI -Complete mitosis exit quiz 10-15 min

19. Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase

20. Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase

21. Mitosis Exit quiz 10-15 minutes