2. Mitosis

3. Mitosis (Animal Cells)
After “S” phase replicates DNA
Division of nucleus ONLY ! chromosome # stays constant
Centromere divides  each chromatid becomes a daughter chromosome
M checkpoint-stops if chromosomes not aligned
Prophase
Metaphase
Anaphase
Telophase

4. Chromosome Number
Each species has unique chromosome # no relationship to complexity
Diploid--2n  2 copies of each chromosome (1/Mom & 1/Dad) (Homologous pairs)
All somatic cells (body cells) are 2n
Haploid--1n  1 copy of each chromosome (either Mom’s or Dad’s)
Only gametes (sperm/eggs) are 1n

5. Chromosomes
DNA replicates during “S” phase  remains connected at centromere (Sister chromatids)
Chromatin (DNA) wraps around histones (protein “balls”)
* DNA/histone “complex” (nucleosome) supercoils  chromosome
Chromosomes-condensed rod- shaped DNA molecules during division

6. Chromatin!

7. 6 ft of DNA in one microscopic cell = MESSY!!!

8. Histone + DNA = nucleosome

9. Nucleosomes coil around each other…..

10. …and keep coiling…
(remember we have 6 whole feet of DNA to coil into a microscopic space!!!)

11. Until we get a Chromosome!!!
This is actually 2 chromosomes! The original & the duplicated! We call this the replicated chromosome…made out of sister chromatids (exact copies) held together by a centromere.

12. Prophase 5 “events” everything gets ready to divide!!
Chromatin coils  chromosomes appear
Nucleolus disappears
Nuclear membrane disappears
Centrioles & asters appear  move to opposite poles of cell
Spindle fibers appear
Polar fibers  centriole to centriole
Kinetochore fibers  centriole to centromere

14. Metaphase
Kinetochore fibers push chromosomes to middle of cell

16. Anaphase
Kinetochore fibers separate  break centromeres  pull chromatids to opposite poles of cell
Characteristic “V” shape

18. Telophase
Reverse of Prophase

21. Mitosis—Plant Cells Mitosis in plant cells Same phases as animal cells
Plants don’t have centrioles or asters

22. Mitosis in Prokaryotes
Asexual reproduction (Binary Fission)  Cloning
2 identical daughter cells
Single DNA strand duplicates  cell elongates, pinches in half