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 from dad and one from mom 2 sex chromosomes Body cells (somatic) Haploid Cells 1 set of chromosomes 1 sex chromosome Sex cells » Egg » Sperm

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 -cytoplasm and nucleus divides. -two types of cell division in eukaryotes, mitosis and meiosis. -Mitosis results in the production of two new identical cells containing a full set of DNA material. -Meiosis results in the formation of gametes 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:

13. 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.