1. Chromosomes and Cell Cycle

2. Eukaryotic Chromosomes
Made of DNA and protein
Function is to pass on traits

3. When a cell is not dividing, chromosomes are long, thin strands
Before division, they get short & thick and form chromosomes
Structure of chromosome:

4. Each organism has a characteristic # of chromosomes
Ex. Humans have 46 chromosomes
Sexually reproducing organisms have 2 sets with same type of genetic info

5. Our 46 chromosomes exist as 23 pairs

6. Vocabulary Genes: Sections of chromosomes
Chromatin: DNA + Proteins that make up chromosomes
Centromere: The middle of the chromosome that holds the two sister chromatids together

7. Genes are Sections of Chromosomes

9. Chromosome Structure Video

10. Cell Division
Before a cell divides, the cell must be fully mature and DNA must be copied
Then, specialized structures are copied and/or made:
Centrioles – help to make spindle fibers
Spindle fibers – move chromosome

11. Mitosis Division of the nucleus Occurs in 4 stages: PMAT
Prophase
Metaphase
Anaphase
Telophase

12. Cell division occurs in a series of stages, or phases.

13. 1st: Interphase Chromosomes are copied (# doubles)
Chromosomes appear as threadlike coils (chromatin) at the start but each chromosome and its copy (sister chromosome) change to sister chromatids at the end of this phase.

14. Interphase

15. 2nd: Prophase Mitosis begins and cell begins to divide
Centrioles appear and begin to move to opposite ends of cell
Spindle fibers form from the centrioles

16. Prophase

17. 3rd: Metaphase
Chromatids or pairs of chromosomes line up at the center of the cell and attach to the spindle fibers

18. Metaphase

19. 4th: Anaphase
Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell

20. Anaphase

21. 5th: Telophase Two new nuclei form around the chromosomes
Chromosomes become chromatin (threads rather than X’s)
Mitosis ends

22. Telophase

23. 6th: Cytokinesis
Cell membrane pinches inwards to create two daughter cells – each with its own nucleus with identical chromosomes

24. Cytokinesis