Cell division involves DNA replication and chromosome separation to form new cells. Mitosis produces two daughter cells with identical genetic material for cell growth and replacement. Meiosis produces gametes with half the normal chromosome number through two cell divisions, resulting in genetic diversity in offspring from sexual reproduction.

1. Cell Division

2. DNA DNA – large molecule that stores hereditary (genetic) information. - found in the nucleus of a cell . - controls cell division .

3. Chromosomes Chromosomes – MANY strands of DNA wound together into threadlike structures.

4. Cell Division Cell Division – a cell that is dividing into two new cells. - the two new cells are daughter cells .

5. Mitosis Mitosis – two daughter cells with exact same genetic material (DNA) are produced. - daughter cells have same number of chromosomes as parent cell . 6 chromosomes 6 chromosomes 6 chromosomes

6. Interphase Interphase – preparation stage BEFORE Mitosis where the cell grows and duplicates materials. - Longest stage of Cell Cycle - Copies chromosomes ! - Organelles double.

7. Prophase Prophase – first phase of Mitosis where DNA winds into chromosomes .

8. Prophase Chromosomes

9. Metaphase Metaphase – chromosomes line up along the middle of the cell.

10. Metaphase Chromosomes Middle (equator) of cell

11. Anaphase Anaphase – chromosomes are “ pulled ” apart! - move to opposite sides of cell.

12. Anaphase Single Chromosome

13. Telophase Telophase – “ ending ” phase of Mitosis. - two new cells form.

14. Telophase New nuclei Chromosomes unwinding

15. End Results of Mitosis 4 chromosomes at start Chromosomes double into 2 strands (8) 4 chromosomes in each new cell at end

16. What kinds of cells do Mitosis? Single-celled organisms - mitosis as a form of asexual reproduction. Multicellular organisms - mitosis in repair and replacement of body cells (hair, skin, etc.)

17. Cancer: Uncontrolled Division Normal cells will stop dividing when they come in contact with other cells . Cancer – disease where cells do not stop dividing and ignore signals from other cells.

18. What is the Purpose of Reproduction? To form new individuals ( offspring ) of a species . 2 Types: Asexual Reproduction – reproduction involving only one parent. Sexual Reproduction – reproduction involving two parents.

19. Asexual Reproduction Offspring are identical and contain same amount of genetic material as parents . - Results from mitosis . Ex: a. Budding b. Binary Fission c. Vegetative Propogation d. Sporulation e. Regeneration

20. Sexual Cell Division: Meiosis

21. Chromosome Number Human body cell – 46 chromosomes Arranged in 23 pairs (23 X 2=46). Homologous Chromosomes – a pair of chromosomes with same size, shape, etc.

22. Diploid Diploid – body cells that contain two sets of chromosomes. - Ex: skin, hair, heart, liver, muscle cells, etc. - Written as 2n .

23. Haploid Haploid – gamete (sex) cells which contain only one set of chromosomes. - Ex: sperm/egg cells. - Written as n .

24. Meiosis Meiosis – type of cell division used to produce gametes (sex cells). Two functions: Forms cells with half the number of chromosomes. (23 chromosomes in both egg and sperm) Rearrange chromosomes for genetic differences from parents ( variability ). Two sets of phases whereas Mitosis only has one set.

25. Meiosis Overview 4 Chromosomes 2 Chromosomes in each cell

26. Meiosis in Males Meiosis in males produces four sperm (n) cells which are all functional. 2n n n n n

27. Meiosis in Females Meiosis in females produces four egg (n) cells . Only one is functional! 2n n n n n

28. Meiosis = Genetic Variation Meiosis is responsible for genetic differences in new cells: Chromosomes lineup in different ways. Crossing over – swapping pieces of chromosomes.

29. Mitosis Vs. Meiosis Mitosis Meiosis # of parent cells 1 2 # of cells produced 2 4 Appearance of Identical Different offspring Types of cells Body Gametes (egg/sperm)

31. Meiosis I Interphase I – DNA is unwound as chromatin. - DNA duplicates.

32. Prophase I –chromosomes become visible and double-stranded. - Homologous chromosomes pair up. - Crossing over – pieces of chromosomes are swapped. Homologous chromosomes Homologous chromosomes Meiosis I

33. Metaphase I – pairs of homologous chromosomes lineup in the middle of the cell.

34. Anaphase I – homologous chromosomes separate ( not into single-stranded chromosomes or chromatids ).

35. Telophase I – two haploid daughter cells are formed. - nuclear membrane returns!

36. Meiosis II (like Mitosis) Prophase II – two haploid daughter cells now enter meiosis II. - cell has completely divided and chromosomes are separated.

37. Metaphase II – chromosomes (non-homologous) line up in the middle of each cell.

38. Anaphase II – double-stranded chromosomes split into single-stranded chromosomes ( chromatids ).

39. Telophase II – four haploid cells are formed each with single-stranded chromosomes ( chromatids ).