Cell Reproduction: Understanding the Cell Cycle, Mitosis, and Meiosis

1. CELL REPRODUCTION SB1. Students will analyze the nature of relationships between structures and functions in living things a. Explain the role of cell organelles for both prokaryotic and eukaryotic cell in cell reproduction

2. LEQ: What are the four main stages of the Cell Cycle?

3. Cell Reproduction • Each organism has a specific number of chromosomes • Made of DNA store/transfer genetic info • If the chromosome number is not maintained from generation to generation, mutations may evolve. • Humans have 46 chromosomes

4. Cell Reproduction • Two types of cell division maintain chromosome number from generation to generation: • Mitosis • Meiosis

5. MITOSIS • Process by which a cell divides its nucleus and contents • Produces identical diploid cells • Cell that contains two copies of each chromosome, one from mother and one from father. • Occurs in somatic (body) cells

6. The cell cycle is a regular pattern of growth, DNA replication, and cell division The cell cycle has four main stages Gap 1 (G1) DNA Synthesis (S) Gap 2 (G2) Mitosis (M) Cell Reproduction Cell Cycle INTERPHASE

7. The Cell Cycle4 Stages Main Stages: • Gap1 (G1) • Cell growth & normal functions • DNA synthesis (S) • Copies DNA • Gap2 (G2) • Additional growth, DNA checkpoint • Mitosis (M) • Includes division of cell nucleus (mitosis) and division of cytoplasm (cytokinesis) • Only occurs if the cell is large enough and the DNA is undamaged.

8. Interphase prepares the cell to divide (G1, S, G2) During interphase, the DNA is duplicated. Interphase is followed by Mitosis and cytokinesis (M) Mitosis and cytokinesis produce two genetically identical daughter cells. Parent cell centrioles spindle fibers centrosome nucleus with DNA The Cell Cycle

9. The Cell CycleMitosis (M) • Mitosis divides the cell’s nucleus in four phases: • Prophase • Metaphase • Anaphase • Telophase

10. The Cell CyclePhases of Mitosis • During Prophase, chromosome condense, nuclear membrane begins to disappear and spindle fibers form. Centrioles Spindle fibers

11. The Cell CyclePhases of Mitosis • During Metaphase, chromosomes line up in the middle of the cell. Metaphase Plate

12. The Cell CyclePhases of Mitosis • During Anaphase, sister chromatids separate to opposite sides of the cell.

13. The Cell CyclePhases of Mitosis (M) • During Telophase, the new nuclei form and chromosomes begin to uncoil. Cleavage Furrow

14. The Cell CycleCytokinesis • Cytokinesis differs in animal and plant cells • Division of cytoplasm • In animal cells, the membrane pinches closed (forms a cleavage furrow) • In plant cells, a cell plate forms to separate cells.

15. Plant Cell Animal Cell The Cell CycleCytokinesis Cell Plate Cleavage Furrow

16. MEIOSIS • Process that divides a diploid cell into haploid cells • Cell that only has one set of chromosomes • Important in forming gametes for sexual reproduction • Sex cells (egg or sperm cell) • Occurs in sex cells of reproductive organs

17. Process of Meiosis • During Meiosis, diploid cells undergo two cell divisions that result in fourhaploid cells • Role of Meiosis: • Reduces chromosome number • Increases genetic diversity

18. Process of Meiosis • Cell go through two rounds of division • Meiosis I • Meiosis II • Each have four phases similar to mitosis

19. Process of Meiosis Meiosis I • Occurs after DNA has been replicated • Divides homologous chromosomes in 4 phases. • Homologous chromosomes are similar but not identical. - Code for same traits homologouschromosomes MOM DAD Anaphase Telophase Prophase Metaphase

20. Process of Meiosis Meiosis II • Divides sister chromatids in four phases. • Sister chromatids are copies of the same chromosome. • DNA is not replicated between meiosis I and II. sister chromatids Prophase II Metaphase II Anaphase II Telophase II

21. Process of Meiosis • Haploid cells created by meiosis develop into mature gametes. • Gametogenesis is the production of gametes. • Differs between females and males

22. Sperm become streamlined and motile Sperm primarily contribute DNA to embryo The egg gets most of the contents; the other cells form polar bodies Egg contributes DNA, cytoplasm, & organelles to embryo Process of Meiosis

23. Mitosis Produces 2 genetically identical somatic cells Produces diploid cells Undergoes 1 cell division Mitosis (PMAT) Meiosis Produces 4 genetically different germ cells Produces haploid cells Undergoes 2 cell divisions Meiosis I, Meiosis II (PMAT1), (PMAT2) Mitosis vs. Meiosis Similar to mitosis, but there are some important differences

24. Concept Check: • Meiosis produces human cells with how many chromosomes? • 44 • 23 • 46 • 15

25. Concept Check 2. Two similar chromosomes that you inherit from your parents ( one from your mother and one from you father) are called: a. homologous chromosomes b. sister chromatids c. sex chromosomes d. homozygous alleles

26. Concept Check 3. Which of the following cell types is diploid? a. sex cell b. gamete c. sperm cell d. zygote

27. Regulation of Cell Reproduction • Cell cycle regulation is necessary for healthy growth. • Internal and external factors regulate cell division

28. The Cell Cycle • Cells divide at different rates. • The rate of cell division varies with the need for those types of cells • Some cells are unlikely to divide.

29. The Cell Cycle • Cell size is limited • Volume increases faster than surface area. • Cell growth is coordinated with division

30. The Cell CycleSurface Area • Surface area must allow for adequate exchange of materials • Cells that must be large have unique shapes

31. The Cell CycleRegulation • External factors include physical and chemical signals • Example: growth factors are proteins that stimulate cell division. • Most mammal cells form a single layer in a culture dish an stop dividing once they touch other cells.

32. The Cell CycleRegulation • Internal factors regulate growth from inside the cell • Two of the most important: • Kinases • Cyclins • Internal factors are triggered by external factors, both of which will affect the cell cycle.

33. Apoptosis is programmed cell death. Normal feature in healthy organisms Caused by a cell’s production of self-destructive enzymes Occurs in development of infants. webbed fingers The Cell CycleRegulation

34. The Cell CycleRegulation • Cell division is uncontrolled in cancer • Cancer cells form disorganized clumps called tumors • Cancer cells do not carry out necessary functions • Cancer cells come from normal cells with damage to genes involved in cell cycle regulation.

35. The Cell CycleRegulation • Benign tumors remain clustered and can be removed. • Malignant tumorsmetastasize, or break away, and can form more tumors.

36. The Cell CycleRegulation • Carcinogens are substances known to promote cancer • Standard cancer treatments typically kill both cancerous and healthy cells.