1. Chromosomes & The Cell Cycle

2. Chromatin & Chromosome Composition Made of: DNA Protein - histones Chromosome Structure (after replication): 2 chromatids – identical chromosomes centromere – holds sister chromatids together p and q arms

3. Chromosome Structure

4. Chromosome Numbers + Types Each species has characteristic number Humans = 46 Chimpanzee = 48 Fruit fly = 8 Two Types: Sex chromosome » Humans = 2 » XX = female » XY = male Autosome (body chromosome) » Humans = 44 » 22 from each parent » Matching chromosomes = homologous chromosomes (one from mom and one from dad)

5. Karyotype Photograph of chromosomes in dividing cell. Taken during metaphase -Like chromosomes are lined up next to each other.

7. Chromosomes and Cells Diploid Cell 2 sets of chromosomes : one set from dad and one set from mom. 2 sex chromosomes - XX (female) - XY (male) Body cells (somatic) Humans have 46 chromosomes. 2n = 46 (humans) Haploid Cells 1 set of chromosomes 1 sex chromosome Sex cells (gametes) -sperm -egg Humans have 23 chromosomes in their sex cells. n = 23 (humans)

8. Cell Division: Prokaryotes -prokaryotes have cell walls but no nucleus and membrane bound organelles. -have a single DNA molecule, circular chromosome attached to the cell membrane. -examples: bacteria -cell division is called binary fission.

9. Binary Fission -results in two new identical cells.

10. Cell Division: Eukaryotes Two types of cell division in eukaryotes: 1. mitosis 2. meiosis Mitosis Function: cytoplasm and nucleus divides resulting in two new identical cells containing a full set of DNA material. Meiosis Function: cytoplasm and nucleus divides resulting in four new cells (gametes) each containing one half the DNA material.

11. The Cell Cycle Interphase G 1 S G 2 *G 0 Cell Division:Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

12. Stages of Mitosis: Prophase: -nuclear envelope starts to break down. -chromatin coils into chromosomes -spindle fibers form from the centrioles

13. Metaphase: -spindle fibers attach to the centromeres of each chromosome. -chromosomes line up at the “equator” of the cell.

14. Anaphase: -spindle fibers pull the chromosomes apart into individual sister chromatids toward each centriole. -the cell begins to elongate

15. Telophase: -spindle fibers and centrioles start to break down. -nuclear envelope starts to reform -chromosomes uncoil back into chromatin -cell continues to elongate forming two new cells

16. Cytokinesis: -the cytoplasm is finally split into two new cells. -cell membranes are completely formed around the two new cells. -two new cells are now in G 1 of Interphase. Blood Lily Mitosis

17. Final Details: Control of Cell Division 1. G 1 checkpoint: proteins control whether or not the cell will divide and whether or not DNA synthesis can proceed. 2. G 2 checkpoint: DNA repair enzymes check the newly replicated DNA. 3. Mitosis checkpoint: if all is good, proteins signal for mitosis to end and cells enter G 1. The proteins that control cell division are coded for by genes. If the gene is mutated, the proteins may be altered. This may lead to cancer.