1. Meiosis Making Gametes

2. Mitosis Review Mitosis: Division of the Nucleus ProphaseMetaphaseAnaphaseTelophase How many times does the nucleus divide in mitosis?ONE

3. Mitosis Review Think in your head: What are the four stages of mitosis? What is the purpose of mitosis? Prophase – Metaphase-Anaphase-Telophase The first purpose of mitosis is growth. The second function of mitosis is repair. Cells are constantly wearing out and getting damaged and unless an organism replaces them at least as fast as they are lost, a gradual deterioration will occur. Slide # 2

4. Meiosis Making Gametes

5. Introductory Vocabulary 1. Somatic cell: body cell a. EX: skin or bone cell 2. Diploid: two sets of chromosomes; 2n a. EX: humans have 2 sets of chromosomes in each body cell; 1 set came from the sperm & the other set came from the egg Slide # 3 Mitosis results in 2 diploid cells Diploid (2n) somatic cell

6. About Meiosis 1. Purpose of meiosis: produce haploid gametes. 2. Haploid: having 1 set of chromosomes; 1n 3. Gametes- special cells used in sexual reproduction. a. EX: egg and sperm cells b. Gametes are ONLY produced by meiosis 4. Meiosis occurs in reproductive organs (ovaries and testes) Slide # 9

7. Overview of Meiosis 1. Interphase: cell duplicates its chromosomes 2. Chromosomes are only duplicated ONCE 3. Cell divides 2 times to produce genetically different 4 cells Slide # 10

8. Stages of Meiosis I Slide # 11

9. Prophase I 1. Chromatids pair up with their Homologous pair forming a tetrad. 2. Crossing over is a process where pieces of two homologous chromosomes switch places. Slide # 12

10. Replicated Chromosome Sister Chromatid Slide # 13

11. Tetrad Maternal chromosome replicated Paternal chromosome replicated Slide # 14 These chromosomes are homologous T tongue rollingt non tongue rolling F1M1

12. Crossing Over: Occurs in Prophase I 1. Homologous chromosomes : a. Pair up alongside each other lengthwise b. Swap bits and pieces of their chromosomes, shuffling the genome 2. Crossing over ONLY happens in Prophase I & results in NEW chromosomes that did not exist before in either parent 3. Why crossing over is important: a. It creates the genetic diversity of ALL sexually reproducing organisms b. Yes, this means you too! Slide # 15

13. Metaphase I: Tetrads line up in center Slide # 13 Anaphase I: Tetrads separate Telophase I & cytokinesis Meiosis I

14. Stages of Meiosis II Slide # 19

15. Meiosis II Slide # 15 Prophase II: Chromatid pairs move to center Metaphase II: The chromatids line up at center of the cell Anaphase II: chromatid pairs separate Telophase II: cells divide, producing 4 haploid cells

16. Meiosis occurs in the testes and is called spermatogenesis and in the ovaries of female and is called oogenesis.

17. Human Inheritance Karyotypes, Nondisjunction, and Chromosome Disorders

18. Karyotypes 1. Karyotypes show the 23 homologous pairs for the person in which the cells were taken. 2. The pairs are put in order from longest to shortest and numbered from 1 to 23. 3. Pairs 1-22 are autosomes. 4. Pair 23 are sex chromosomes What is the sex of this individual? Male

19. Nondisjunction Nondisjunction caused by an error during meiosis I when homologous pairs fail to separate. One gamete will end up with one extra chromosome, and another gamete will be left with one less chromosome.

20. What is aneuploidy? 1.Aneuploidy: When chromosomes fail to separate properly during meiosis, the gamete will have an abnormal number of chromosomes Monosomy: one gamete has 22 chromosomes and the other has 23; the zygote ends up with 45 chromosomes Trisomy: one gamete has 24 chromosomes and the other has 23; the zygote ends up with 47 chromosomes

21. Down Syndrome 1. Cells contain one extra copy of chromosome # 21. 2. This results in: a. characteristic facial features b. short stature c. mental retardation d. shorter life-span e. Increased risk for heart problems, immune system problems, and cancer.

22. Turner Syndrome 1. This female has only one X chromosome. 45,X 2. This results in a. a female who cannot have children because the ovaries do not fully develop. b. Short in stature c. Webbed neck d. Some mental disability

23. Klinefelter Syndrome 1. Results in a male who has one extra X chromosome. 47,XXY 2. This results in a. Sterile b. mental retardation. c. true male, but can have some female characteristics.