1. Bell Ringer What is karyotyping and how is it useful?

2. Nondisjunction The homologous chromosomes, or sister chromatids do not separate properly during cell division. This can happen during Meiosis 1 or Meiosis 2

3. Objectives By the end of today you should be able to -Know the difference between somatic cells and gametes -Identify the difference between a diploid cell and a haploid cell. -Compare the processes of Mitosis and Meiosis

4. You have two types of cells in your body Somatic Cells - body cells - Make up most of your body tissues and organs Germ cells -Cells in your reproductive organs that develop into gametes (sex cells)

5. Every species has a characteristic number of chromosomes per cell. Examples: Humans= 46 chromosomes or 23 pairs Dog= 78 chromosomes or 39 pairs Husk Tomato= 24 chromosomes or 12 pairs

6. Chromosomes 1-22 make up your autosomes ( characteristics not related to your sex) The 23 rd pair of chromosomes are your sex chromosomes. (XX or XY)

7. Sexual Reproduction Involves the fusion of two gametes, resulting in offspring that are a genetic mixture of both parents. This fusion is called fertilization. The nuclei of the sperm and egg cell fuse together to form one nucleus. Since you are taking DNA from 2 cells and creating one you need half the amount of DNA

8. Diploid and Haploid Cells Diploid Cells - The cell has two copies of each chromosome; one from the mother, and one from the father - Body cells -represented as 2n - Humans cells the diploid number is 46 Haploid Cells -A cell has only one copy of each chromosome - Gametes (sex cells) -Each human egg or sperm cell has 22 autosomes and 1 sex chromosome

9. OrganismDiploid (2n)Haploid (n) Human4623 Chimpanzee24 Elephant56 Garden pea14 Turkey40 Polar Bear74 Pineapple25

10. Meiosis Germ cells in reproductive organs undergo the process of meiosis to form gametes. Meiosis is a form of nuclear division that divides a diploid cell into a haploid cell.

12. Objectives -What is the difference between somatic cells and gametes -Identify the difference between a diploid cell and a haploid cell. -Compare the processes of Mitosis and Meiosis

13. Objectives Illustrate the process of meiosis 1 and describe what is happening Describe how crossing over can alter the composition of chromosomes

14. Meiosis l Prophase l -Chromatin  Chromosomes -nuclear membrane breaks down -Homologous chromosomes pair up -Crossing over may occur

15. Meiosis l Metaphase l -Homologous chromosome pairs are randomly lined up along the middle -This mixes up the chromosomal combinations and helps create genetic diversity

16. Meiosis l continued Anaphase l -Paired homologous chromosomes separate -Sister chromatids stay together during meiosis l

17. Meiosis l Telophase l -Nuclear membrane forms again -Spindle fibers disassemble - Cell undergoes cytokinesis End Result is two cells with unique combinations of 23 chromosomes

19. Objectives Illustrate the process of meiosis 1 and describe what is happening Describe how crossing over can alter the composition of chromosomes

20. Objectives Illustrate the process of meiosis and describe what is happening Describe how nondisjunction can alter the number of chromosomes in a cell Distinguish between mitosis and meiosis. Compare and contrast spermatogenesis with oogenesis.

21. There is no Interphase: Chromosomes do NOT duplicate

22. Meiosis ll Prophase ll -Nuclear membrane breaks down Chromosomes condense -Centrioles move to opposite sides of cell -spindle fibers assemble Metaphase ll -Spindle fibers align the 23 chromosomes in the middle -Each chromosome still has 2 sister chromatids

23. Meiosis ll Anaphase ll -The sister chromatids are pulled apart to opposite sides of the cell Telophase ll -nuclear membranes reform -spindle fibers break apart -The cell undergoes cytokinesis

24. Cytokinesis The end result is four haploid cells with a combination of chromosomes from both the mother and the father.

27. Oogenesis Spermatogenesis Oogenesis

28. Nondisjunction- The homologous chromosomes, or sister chromatids do not separate properly during cell division. Meiosis 1 Meiosis 2

29. Objectives Illustrate the process of meiosis and describe what is happening Describe how nondisjunction can alter the number of chromosomes in a cell Distinguish between mitosis and meiosis. Compare and contrast spermatogenesis with oogenesis.